Abstract: A device for gripping and detaching a top nozzle subassembly from the upper end portions of the guide thimbles in a reconstitutable fuel assembly includes a central spider assembly disposable in overlying relation to an upper hold-down plate of the top nozzle subassembly, locating lugs arranged for insertion into coolant flow openings in the hold-down plate, collars interconnected to the spider and being disposed on the locating lugs and bearing on the hold-down plate when the locating lugs are inserted in the flow openings, and elongated studs received through and rotatable within respective central bores defined in the locating lugs. Upon rotation of the studs in one direction, compression of the hold-down springs disposed between the plates relieves the tension on the guide thimble upper end portions whereby the upper end portions are thereby prepared to be severed at locations immediately below the upper limit.

Abstract: A device for unfastening and lifting a top nozzle subassembly from the guide thimbles of a reconstitutable fuel assembly includes hollow gripper tubes having open lower ends, spaced yokes mounting the gripper tubes, pull rods disposed in the gripper tubes, end plugs attached to lower ends of the pull rods and disposed at the open lower ends of the gripper tubes, stop plugs stationarily disposed in the gripper tubes spaced above their open lower ends, elastomer blocks disposed in the gripper tubes between the end and stop plugs, and inner tubes disposed within the gripper tubes about the elastomer blocks. Lower end portions of the gripper tubes are capable of insertion into sleeves of the top nozzle subassembly to positions therein located adjacent to threaded lower ends of the sleeves.

Abstract: A nuclear reactor fuel rod includes a fuel tube and an improved end plug assembly having a pair of hollow end plugs which seal opposite ends of the fuel tube. Each end plug has an outer body portion with an outside diameter substantially the same as the outside diameter of the fuel tube and an inner body portion of reduced diameter inserted into an end of the tube. Each plug has a cavity defined therein which increases the space within the rod for fission gas expansion. An outer region of the cavity within the outer body portion of the end plug is undercut relative to an inner region of the cavity within the inner body portion of the plug. One of the end plugs also has an insert fitted into its inner body portion which prevents fuel chips from falling into the cavity of the end plug. A slot is formed axially in a side wall of the insert which allows communication of gas from the tube into the cavity of the end plug.

Abstract: A soluble burnable absorber rod for a nuclear reactor fuel assembly has a tubular body with a pair of end plugs sealing the opposite ends thereof and defining a chamber within the body. A neutron absorber material in liquid form, preferably boric acid with an enhanced concentration of boron isotope B-10, is contained within the chamber. The tubular body has reinforcing convolutions formed therein for strengthening the body to withstand external pressure acting thereon. Also, one of the end plugs acts as a hydride sink and a hydrogen getter material is disposed adjacent the other end plug.

Abstract: A boiling water nuclear power reactor includes an improved control rod associated with each of its clusters of fuel assemblies. The control rod has an elongated central stem defining a longitudinally extending internal central gas plenum and a plurality of blades orthogonally arranged in pairs to provide a cruciform configuration in which the blades connect to and extend radially outward from the central stem. Each blade incorporates a series of internal cavities arranged in columns and rows across the length and width of the blade, and a neutron absorbing pellet is disposed in each cavity. The cavities communicate with the central plenum so that any gases generated by irradiation of the pellets can expand into the plenum. The cavities and pellets are arranged to form a longer, constant worth section in a body portion of each blade and a shorter, reduced worth section in an end tip portion of each blade.

Abstract: An apparatus for preassembling the components of a top nozzle into a completed subassembly for later mounting on the skeleton of a fuel assembly includes a base having a plurality of bores with spring-loaded pistons disposed in the bores for yieldably supporting extension tubes of the top nozzle. The tubes can vertically move in the bores so that all of the lower retainers on the tubes will be brought into contact with a lower surface of a lower adapter plate for uniformily supporting the plate on the tubes. Also, the apparatus includes a plurality of locating pins insertable through passageways in an upper bearing plate of the top nozzle and into the upper ends of the extension tubes for aligning and guiding the extension tube upper ends into the passageways upon movement of the bearing plate against the bias of a plurality of coil springs which surround the tubes and extend between the lower adapter and upper bearing plates.

Abstract: A control rod with a "reduced worth" tip is provided for a nuclear reactor which includes an elongated tubular cladding with its opposite ends closed and having a plurality of pellets of two different types disposed in its lower end portion in an end-to-end relationship. One type of pellets is formed of a neutron absorbing material, such as B.sub.4 C, whereas, the other type of pellets is formed of an inert material, such as ZrO.sub.2. The absorber pellets and the inert pellets are interspaced between one another in the lower end of the rod so as to gradually reduce the rate of change of the neutron flux experienced at the rod's lower end portion as it moves in and out of the fuel assembly to thereby alleviate pellet-clad-interaction and thus reduce the likelihood of fuel rod failure. In one embodiment, the axial heights of the absorber pellets progressively increase from the bottom to the top of the rod's lower end portion while the axial heights of the interspaced inert pellets remain constant.

Abstract: A top nozzle of a nuclear reactor fuel assembly is removably mounted to the guide thimbles of the fuel assembly by mating and unmating of pluralities of outer and inner sockets defined in the respective top nozzle and guide thimbles. A bearing plate supported on the top nozzle and movable relative thereto between a lower, non-release position and an upper, release position supports a plurality of locking tubes which are inserted at their lower end portions into the outer sockets. When the bearing plate is at its non-release position, the lower end portions of the locking tubes are inserted into the inner sockets and prevent them from unmating from the outer sockets and thereby retain the top nozzle mounted to the guide thimbles. However, when the bearing plate is at its release position, the locking tube lower end portions are withdrawn from the inner sockets and allow them to unmate from the outer sockets and thereby allow lifting of the top nozzle off and removal from the guide thimbles.

Abstract: A fuel assembly for a nuclear reactor is provided with two access plugs in the adapter plate of the top nozzle whereby selected fuel rods can be removed and replaced without disassembling the assembly and while the assembly is in place in its operating position in the core region.

Abstract: A top nozzle subassembly having a hold-down device incorporated therewithin is provided for a nuclear reactor fuel assembly. The subassembly is slidably mounted on the upper ends of the control rod guide thimbles and is removably attached by internally threaded collars which threadably mate with external threads provided on the upper ends of the guide thimbles. Unthreading of the collars allows the subassembly to be removed from the fuel assembly to gain top access to the fuel rods within the fuel assembly. The invention also includes a special tool for threading and unthreading of the collars.

Abstract: A leak detector has a gas probe 1 for sensing signal gas escaping from an enclosure containing that gas at a pressure slightly in excess of ambient surrounded by a curtain of barrier gas. The reading of a gas analyzer such as a mass spectrometer depends on the height of the probe from the surface. A height sensor is attached to the leak detector and a programmable amplifier 6 contains information on the characteristic curve of the gas sensor. An output signal from the programmable amplifier compensates for the height of the probe from the surface being detected. The speed of the leak detector can be corrected for in the same way.

Abstract: The leak detector comprises an annular chamber 11 which leads to a circumferential orifice 14 which in turn leads to an annular duct 21 which is symmetrical about the axis of the detector. Barrier gas is fed to the annular chamber 11, for example from an annular chamber 18 and emerges from the opening 20 to form a substantially laminar flow. Leaks are detected by means of a signal gas within an enclosure at a pressure slightly in excess of ambient, and the signal gas is detected from leaks via a probe 2 which is connected for example to a mass spectrometer. The curtain 1 is stable and enables uneven surfaces to be tracked.

Abstract: A method of reconstituting a nuclear reactor fuel assembly having a top nozzle subassembly attached to the upper end of its control rod guide thimble wherein the subassembly includes an upper hold-down plate, a lower adapter plate, and a coils spring interposed between the two plates. A force is applied on the hold-down plate to compress the coil spring and transform the subassembly from its operation mode to a reconstitution mode. The wall of the thimble is severed just below a first attaching retainer mounted on the end of the thimble which defines the upward limit movement of the hold-down plate during the operation mode. Containing fingers are placed on the subassembly for removing it as a contained unit. The top nozzle subassembly or a new replacement subassembly is then replaced on the severed thimble in its reconstitution mode and a second attaching retainer is mounted on the upper end portion of the severed thimble in redefining the upward limit movement of the hold-down plate.

Abstract: A method of, and apparatus for, detecting leaks from a surface provides a sampling device (10) making use of an air curtain (C). The body (11) of the device (10), the curtain (C) and a surface (B) to be tested together define a sampler volume (S). Pressure in the sample volume (S) is regulated to draw signal gas from a source thereof to the volume (S) along leak path (L) which exists. Sampled gas is withdrawn from the volume for checking by means of a mass spectrometer (18) for the presence of signal gas.

Abstract: A displacer rod for use in a mechanical spectral shift pressurized water nuclear reactor comprises a sectioned substantially hollow low neutron absorbing metal rod capable of displacing reactor coolant without absorbing a high amount of neutrons. The tubular sections can be made of stainless steel or Zircaloy tubing and may contain pellets for weighting the displacer rod.

Abstract: A distributed processing telex switch having different levels of processor control to handle the calls between terminations connected to the exchange is disclosed. A common control processor occupies the highest level of processor control and function as the system-wide manager. Next below common control is a plurality of master control processors which function to switch the command data between common control and the lower levels of processor control, and to handle the conversation data generated by each of the terminations connected to the exchange. Each master control processor controls a predetermined number of termination from among all of the terminations connected to the exchange. Connected to each master control processor is a plurality of group control processors which control the flow of data to and from a second predetermined number of terminations from among the terminations controlled by each master control processor.

Abstract: A fluid heating system specifically designed for the use of solid bulk fuel, such as wood or the like. The burner unit includes a continuous coil of fluid carrying conduit which acts both as a grate for supporting the fuels of combustion and as the primary implement for circulating fluids in close proximity to the combustion material so as to maximize the heat absorption by the fluid. Primary and secondary combustion air inlets combine with a baffling system that maximizes the efficiency of the combustion process within the heat transfer coil. Room heating and hot water storage apparatus are also disclosed as desirable end uses for the heated fluid.

Abstract: An electrode assembly for electro-chemically machining an article, such as an aerofoil shaped blade for a turbo machine. The assembly comprises a plurality of electrodes 2,3 for location adjacent a workpiece 7. Each electrode 2,3 is constrained to move in a first direction towards each other and towards the workpiece 7 and has two side members 22,23 carried by a main body 21. The side members 22,23 are constrained to move with the main body 21 and also relative to the main body in directions parallel to the first direction. The side members 22,23 advance ahead of the main body 21 and when they abut the side members 22,23 of the other electrodes 2,3 their advancement is stopped while the main bodies 21 of the electrodes 2,3, continue to approach each other for a predetermined distance. In this way edge effects during machining are eliminated enabling an accurate shape of article to be produced.

Abstract: In a Telex switching system line terminator unit having means to transmit a character from the terminator to its terminal, in which the character is transmitted in a serial mode and terminated by a stop bit, an improvement in the manner of generating the stop bit is provided. A variable length stop bit is dynamically generated for each character transmitted such that the length of the stop bit is changed as the time required by the calling terminal to transmit the character to its terminator unit decreases over that required by the called terminator unit to transmit the character to the called terminal. Patterns in the rate of transfer of characters from the calling terminator unit to the called terminator unit are monitored to control the length of the stop bit.

Abstract: A readily assembled self-supporting structure for carrying an antenna and associated electronics apparatus includes a tripod base having support means for pivotably supporting a top mast on which the antenna and associated apparatus are mounted. Pivotably joined with the support means, a mast engaging member is adapted to swing in a predetermined direction to either raise or lower the mast. A heavy battery pack used to power the apparatus is pendulously suspended from the member below the support means and stabilizes the structure against wind forces without requiring ground anchors. In addition, the battery pack acting about the pivot erects the top mast in a perpendicular attitude irrespective of the slope of the antenna site. The structure is held rigid by means of three guys between the top of the mast and the feet of the tripod.