Abstract: A nuclear fuel assembly includes and upper yoke, a base, an elongated, outer flow channel disposed substantially along the entire length of the fuel assembly and an elongated, internal, central water cross, formed by four, elongated metal angles, that divides the nuclear fuel assembly into four, separate, elongated fuel sections and that provides a centrally disposed path for the flow of subcooled neutron moderator along the length of the fuel assembly. A separate fuel bundle is located in each of the four fuel sections and includes an upper tie plate, a lower tie plate and a plurality of elongated fuel rods disposed therebetween. Preferably, each upper tie plate is formed from a plurality of interconnected thin metal bars and includes an elongated, axially extending pin that is received by the upper yoke of the fuel assembly for restraining lateral motion of the fuel bundle while permitting axial movement of the fuel bundle with respect to the outer flow channel.

Abstract: Apparatus and method for directing a controlled number of laser pulses onto a work piece to be machined. More specifically, the laser machining apparatus includes an excitable laser and an excitation lamp for continuously exciting the laser to emit a sequence of laser pulses. The application of the laser pulses to the work piece is controlled by an inner-cavity shutter that is opened to permit a precise number of pulses to be directed onto the work piece. The frequency (REP RATE) and pulse width of the laser pulses are controlled by the excitation lamp and, in turn, are set to create a progressive weld of significant depth and structural integrity. In particular there is provided control means for counting the number of laser pulses applied to a machining site of the work piece, whereby a known controllable quantity of energy is imparted to each site.

Abstract: A welding fixture for a nuclear fuel assembly grid having rigid top and bottom members and having apparatus for releasably securing them together. The bottom and top members each have an egg-crate configuration of interleaved fixture straps. Top notches on the bottom fixture straps' top edges are placed to engage the grid straps' bottom edges when the grid straps are aligned for welding. Likewise, bottom notches on the top fixture straps' bottom edges are placed to engage the grid straps' top edges when the grid straps are aligned for welding.

Abstract: Apparatus and method for testing TIG (tungsten inert gas) welds of end plugs on a sealed nuclear reactor fuel rod. An X-ray fluorescent spectrograph testing unit detects tungsten inclusion weld defects in the top end plug's seal weld. Separate ultrasonic weld inspection system testing units test the top end plug's seal and girth welds and test the bottom end plug's girth weld for penetration, porosity and wall thinning defects. The nuclear fuel rod is automatically moved into and out from each testing unit and is automatically transported between the testing units by rod handling devices. A controller supervises the operation of the testing units and the rod handling devices.

Abstract: A self-sealing electrode guide for supporting an electrode in an electrode port of a welding chamber, includes a housing adapted to be mounted in the electrode port and a sealing sleeve accommodated in a housing channel defined in the housing. The sealing sleeve has opposite first and second ends and an open-ended passage adapted to receive the electrode. The first end is disposed for exposure to an external force which is oriented in a direction extending from the first end towards the second end and which is derived from a pressure in the welding chamber. An abutting arrangement is provided in the housing for cooperating with the second end to prevent displacement of the sealing sleeve relative to the housing. The sealing sleeve is resiliently deformable by the external force for assuming a deformed state in which the sealing sleeve is sealingly pressed about the electrode and against housing walls forming the housing channel.

Abstract: A computer controlled apparatus is disclosed for controlling a sequence of machine steps utilizing a laser beam whose power level is adjusted in accordance with its parameters as a function of a measurement of the power level of the generated laser beam. The laser apparatus includes a laser source or rod for emitting a laser beam and means in the illustrative form of a laser lens assembly for focusing and directing the laser beam onto the work piece. The laser source is associated with excitation means in the form of lamps for pulse driving or exciting the laser rod to emit a like sequence of laser pulses, whose parameters, e.g. pulse width and frequency, are selectively varied and controlled. The power level of the laser beam is calibrated by first measuring the power level of the laser beam as directed onto the laser piece, and then by using the measurement of laser power to calibrate or to adjust the degree of lamp excitation.

Abstract: An individual nuclear fuel rod weighing system for rods carried on a tray which moves along a materials handling conveyor. At a first tray position on the conveyor, a lifting device raises the rods off the tray and places them on an overhead ramp. A loading mechanism conveys the rods singly from the overhead ramp onto an overhead scale for individual weighing. When the tray is at a second position on the conveyor, a transfer apparatus transports each weighed rod from the scale back onto the tray.

Abstract: To remove the bottom nozzle of a nuclear fuel assembly, the nozzle plate must be disconnected from the control-rod thimbles. For nozzles whose control-rod thimbles are connected to the nozzle plate by screw fasteners having lock pins welded to the nozzle plate, a cutter for severing the welds is provided. The cutter is rotated by a motor at the work position through a long floating shaft. A long feed shaft operated by a thumb nut at the work position feeds the floating shaft and cutter downwardly through the weld. The bushings extend from a bushing plate, each encircling a screw fastener. Each bushing has a yieldable sleeve for sealing the region around a screw fastener to trap the chips from the severed weld. The cutter is indexed from weld to weld by indexing plates. To remove chips adhering to the cutter, the suction tube of a suction-pump-operated eductor is inserted in the auxiliary hole and the cutter is inserted in the bushing and chips are removed by suction.

Abstract: A welding fixture for use in welding sleeves to a grid includes a plate having a pair of spaced pins with bushings for both locating the grid and positioning a sleeve, and abutment members; and a plurality of sleeve locating positioning pegs. A method of positioning a grid and sleeves for welding sleeves to the grid.

Abstract: Method of making a burnable neutron absorber of boron carbide in a matrix of aluminum oxide. In the practice of this method, boron-carbide particles are coated with a pore former and then they are mixed in a slurry with aluminum oxide powder. When the slurry is subsequently dried and sintered, the pore former is burned out and a body is formed including the boron-carbide particles in a matrix of aluminum oxide with substantially all boron-carbide particles in the body surrounded by a void.

Abstract: Apparatus is disclosed for laser machining a work piece comprising a laser lens adapted to be releasably mounted to permit cleaning of the lens to remove any debris collected thereon during laser machining. The mounting includes a cylindrical base for defining a path along which the laser beam emitted by the laser source is directed onto the work piece, and a mounting member for mounting the laser lens with respect to the cylindrical base and adapted to be removably mounted on the cylindrical base in a manner whereby the lens is disposed to a certain position with respect to the cylindrical base. To this end, there is included a locking member engaging the cylindrical base and biasing the mounting member and its laser lens to the certain position with respect to the cylindrical base.

Abstract: A tool (30) for facilitating insertion or removal of a C-shaped spring clip in a burnable poison rod, or the like, includes an outer member (38) secured to a front handle (32) and an inner member (40) extending through the outer member and the front handle which is connected to a coaxial rear handle (34). The handles (32, 34) are interconnected for relative rotation by means of a set screw (64) and circumferential groove (56). The distal ends of the inner and outer members (38, 40) are notched to receive the spring clip and engage it for compression. Provided between the handles (32, 34) is a locking and release assembly (42) and an adjustable positioning ring (58) by which the spring clip can be compressed, locked in compressed condition for insertion, and then released in the desired position before withdrawing the tool.

Abstract: Apparatus for applying a vacuum to a nuclear fuel rod cladding tube's interior through its open end while girth welding an inserted end plug to its other end. An airtight housing has an orifice with a seal which can hermetically engage the tube's open end. A vacuum hose has one end connected to the housing and the other end connected to a vacuum pump. A mechanized device moves the housing to engage or disengage its seal with the tube's open end. Preferably the mechanized device includes an arm having one end attached to the housing and the other end pivotally attached to a movable table; an arm rotating device to coaxially align the housing's orifice with the welding-positioned tube; and a table moving device to engage the seal of the coaxially aligned orifice with the tube's open end.

Abstract: Laser machining a work piece in an environment that is non-reactive to the material of which the work piece is made. In particular, the laser machining apparatus includes a chamber for readily receiving a work piece and means for moving the work piece along its X, Y, and Z axes with respect to the laser beam, while maintaining the purity of the machining environment. To this end, the machining chamber is mounted upon means for driving the machining chamber along X and Y axes. The machining environment is maintained within the machining chamber and a sealing means taking the form of a plate having a substantially flat surface, that is disposed of a substantially uniform distance from the peripheral edge of the machining chamber, so that the machining chamber may be driven without resistance by the moving means.

Abstract: Selected isotopes of zirconium are separated by irradiating vapor of material consisting of hydrolysis-resistant compounds dicyclopentadienyl zirconium dichloride, dicyclopentadienyl zirconium di-isopropoxide and/or dicyclopentadienyl zirconium di-tert-butoxide with a laser beam tuned to vibration of an excitable band of the component of the compounds including the selected isotope. The component of the material including the excited band is separated from the remainder of the material. Parts for a nuclear reactor are made of zirconium derived from the separated material or from the remainder, whichever has the lower neutron-absorption cross section.

Abstract: A laser machining apparatus is disclosed as including a bed lying on a floor surface for supporting a source of a laser beam with respect to a work piece supported upon the bed. The bed is of a rigid construction and defines a substantially planar, reference surface for supporting at least one machining chamber for receiving and establishing about the work piece an environment that is non-reactive to the material of which the work piece is made. A work piece housing is fixedly attached to the reference surface for defining a second, substantially planar sealing surface with respect to the reference surface. An adjusting mechanism in the illustrative form of a finely threaded screw serves to accurately position the machining chamber and in particular a peripheral flange thereof to provide a uniform gap between the peripheral flange and the sealing surface in a manner to permit ready movement of the machining chamber with respect to the sealing surface.

Abstract: Apparatus and method for preventing the rotation of one or more elongated rods used in nuclear fuel assemblies include an end plug secured to one longitudinal end of such an elongated rod and having an out-of-cavity, non-round structure affixed thereto and configured to mate with a complementary shaped structure in a lower tie plate of a nuclear fuel assembly in such a manner as to prevent the rotation of the rod about its longitudinal axis. In one embodiment, the end plug includes a pair of flats formed on a portion of the end plug and configured to abut against a pair of flats formed on the outer surface of a cylindrical boss or sleeve of the lower tie plate, thereby to prevent the rotation of the rod. In another embodiment, four grooves, disposed 90.degree. apart about the periphery of an end plug of a rod form a spline. The grooves are configured to receive four, radially inwardly protruding, key members disposed 90.degree.

Abstract: Welding plates for laser beam welding of a fuel rod grid are provided, each welding plate having a surface with a set of equally spaced, parallel grooves and with a second set of such grooves perpendicular to the first set. Each of the welding plates is provided with openings therethrough at the points of intersection of the straps forming the grid, so as to expose those points of intersection to a laser beam for laser beam welding of the points of intersection. A vane side welding plate has the walls of the laser beam access openings placed so as to hold vanes extending from the straps in deflected position. Stand-off pins and clamping bolts are provided, the latter having heads with access openings for the laser beam. The welding plates are provided with protrusions which extend laterally thereof, the protrusions having precisely located holes with precision bushings therein.

Abstract: Apparatus and method are disclosed for machining and, in particular, welding a work piece in an environment comprised of a gas non-reactive to the material of the work piece to minimize the contamination of the welds effected on the work piece. In an illustrative embodiment of this invention, there is provided a welding chamber for receiving the work piece and for establishing the welding environment therein. The welding chamber has an input port disposed in a bottom portion thereof, that is coupled to means in the form of a controllable pump for directing or pumping the non-reactive or inert gas, e.g. argon, through the input port and into the welding chamber. The welding chamber also includes an output port, whereby the non-reactive gas may escape from the welding chamber.

Abstract: A nuclear reactor fuel assembly spacer grid. The grid straps form an egg crate configuration creating standard cells to enclose the fuel rods. The standard cells have at least one of their straps with an integral spring portion extending into the standard cell and pushing against the fuel rod. A distinct backup spring is positioned transverse to and behind each of the spring portions of the straps and is positioned so as not to touch the fuel rods. The straps are made of a material having a low neutron capture cross-section while the backup spring is made of a material having good radiation stress relaxation properties.