Abstract: A rod straightness measuring system and method. A rod, such as a nuclear fuel rod, is supported and rotated in such a manner that if the rod were straight, it would be rotated about its longitudinal axis and remain straight without transverse translational motion, and in such a manner that if the rod were cambered, it would remain so cambered while supported and rotated. A multiplicity of separated and fixed range finders are placed apart from and directed towards the rod so that they would be directed perpendicular to a straight rod's longitudinal axis. The range finders measure the distance to the rotating rod. Differences in maximum and minimum measurements for each range finder indicate the degree of straightness of the rod. In a preferred system and method, the range finders are placed at known distances from a straight rod, and differences in distance measurements from the known distances for each range finder indicate the degree of rod straightness.

Abstract: A burnable absorber coated nuclear fuel. A fissionable material nuclear fuel substrate is at least partially covered by a burnable absorber layer. A hydrophobic material overcoat layer generally covers the burnable absorber layer and is bonded directly to it.

Abstract: A method for coating a nuclear fuel with a burnable poison and a burnable poison coated nuclear fuel made by the method. The nuclear fuel is surface cleaned, and then a burnable poison layer is sputtered thereon. A sputtering deposition rate is picked that preferably will heat the nuclear fuel surface between 200.degree. C. and 600.degree. C. For deposition rates that result in heating the nuclear fuel surface to less than 200.degree. C., external heat is applied to heat the nuclear fuel surface between 200.degree. C. and 600.degree. C. To make the burnable poison layer less hygroscopic, an overcoat layer of a hydrophobic material is sputtered on the burnable poison layer.

Abstract: A system for identifying a bar code label affixed to a rod wherein the bar code label including each bar thereof generally circumferentially spans on the rod an angle (the bar code angle) greater than 180.degree. and less than 360.degree. about the rod's longitudinal axis. The system includes a bar code reading optical scanner and a rod positioning mechanism. The scanner has a light beam from a single source and creates two scanning lines which superimposingly intersect at an angle which is greater than 360.degree. minus the bar code angle and which is less than or equal to 180.degree.. The rod positioning mechanism colinearly (or close enough to such) aligns the rod's longitudinal axis with the intersection line of the scanning lines so that the bar code label may be identified independent of the rotational position of the rod about its longitudinal axis.

Abstract: A nuclear fuel spacer grid with improved outer straps. The grid has an egg-crate array of interleaved grid straps creating cells for enclosing the fuel rods. The grid also has four outer straps connected together in a square-shaped array surrounding the grid strap's heightwise edges. The outer straps have a central portion to which is attached the grid straps' heightwise edges. The outer straps also have a top and a bottom resilient lengthwise border portion extending vertically beyond and horizontally outwardly beyond their associated outer straps central portions.

Abstract: A nuclear fuel spacer grid with improved grid straps. The grid has an egg-crate array of interleaved grid straps creating cells for enclosing the fuel rods. Near beginning of life in the reactor, the grid straps bend in a spring-like manner to flexibly grip the fuel rods with their preferably rigid protrusions. In a cell, the protrusions on two non-opposing grid straps are closed to longitudinal coolant flow while the protrusions on the remaining grid straps associated with the cell are open to such flow. Near end of life the grid straps loose resiliency due to irradiation--induced stress relaxation and the fuel rod has a loose fit against the protrusions due to radiation effects. However, the fuel rod is held in position in the cell by the coolant flow therethrough which forces the fuel rod away from the closed protrusions and into contact with the open protrusions. The protrusions in one cell are coplanar. The protrusions in the cells lie in one of two longitudinally separated planes.

Abstract: The present invention relates to a sensing apparatus for sensing the displacement of a movable object relative to its ideal vertical path of travel. The apparatus includes two elongate reference wires extending parallel to the ideal vertical path of travel of the object. The apparatus further includes two sensing devices mounted for movement with the object. Each of the sensing devices is normally positioned a predetermined distance from a respective one of the reference wires such that engagement of the reference wire by the sensing device indicates that the object has been displaced about or from its expected predetermined path of travel.

Abstract: A method for coating a uranium dioxide nuclear fuel with a zirconium diboride burnable poison. First, a layer of niobium is bonded to the nuclear fuel. Then, a layer of zirconium diboride is deposited by chemical vapor deposition on the niobium layer. A zirconium diboride coated nuclear fuel having a layer of niobium between a uranium dioxide substrate and the zirconium diboride layer also is disclosed.

Abstract: A nuclear reactor fuel assembly spacer grid having grid straps and a first type of spring clip. The grid straps define standard cells enclosing fuel rods and thimble cells enclosing control rod guide thimbles. The spring clip is bent to widthwise encircle a grid strap and has its two ends welded together. The first type of spring clip is used at a location on a grid strap having a standard cell and an adjacent thimble cell. The spring clip has a spring portion compressibly contacting the fuel rod in the standard cell. The spring clip also has a pair of separated flat portions straddling the control rod guide thimble in the thimble cell so as not to interfere with the guide thimble. The spring clip is made of a material having good radiation stress relaxation properties.

Abstract: Elongated tubular elements containing burnable absorber material are clustered in an array to provide a burnable absorber assembly for insertion within one or more guide thimbles of a fuel assembly for controlling reactivity. The burnable absorber assembly, in alternative embodiments, include three tubular elements in triangular relationship and four tubular elements in rectangular relationship. The use of the burnable absorber assembly within the guide thimbles of a fuel assembly results in increased core thermal margin, minimization of end of cycle reactivity penalty, increase in operating cycle length before required refueling, and the ability to utilize burnable absorber assemblies having different strengths at different locations within the fuel assembly for controlling fuel assemblies having significant power gradients, as well as finer control of radial powered distribution and thus achieving lower peaking factors.

Abstract: A partial grid structure is provided for a nuclear reactor fuel assembly for selectively mounting either means for deflecting the upwardly flowing coolant or means for laterally supporting the fuel rods, or both, to substantially eliminate localized neutron flux peaking and thereby increasing the power output of the assembly. The grid structure extends across only a portion of the fuel assembly and is associated with a selective group of fuel rods defined by a predetermined number of the fuel rods contained within the fuel assembly. The grid straps form an egg-crate configuration creating cell openings for receiving the fuel rods of a predetermined fuel rod group. In an alternate embodiment, the fuel rods of the fuel assembly are partitioned into separate groups by the use of separate partial grid structures which are combined to form a grid structure assembly.

Abstract: The specification discloses a device (32) for raising peripheral fuel rods of a fuel assembly for inspection under submerged conditions in a nuclear reactor facility. The device (32) includes a frame comprising top and bottom plates (36, 38) interconnected by rods (40) with an intermediate plate (52) supported therein for vertical movement responsive to a cylinder (60). A yoke (64) is mounted for horizontal movement on the intermediate plate (52) responsive to another cylinder (66) to engage a fuel rod so that it can then be lifted by the first cylinder (60). Proper alignment relative to the peripheral rods of the fuel assembly is accomplished by means of pins (50) which are received in indexing holes (80) of a support plate (68) for the fuel assembly.

Abstract: A nuclear reactor system in which the neutron-energy spectrum is displaced towards lower energy (enthalpy) by a control selectively operable by commands outside of the reactor. The core of the reactor contains, in addition to fuel assemblies, sealed tubes filled with helium. The selective control of the neutron energy spectrum includes a master cylinder having a master piston. The master cylinder is immersed in the coolant and admits the coolant through a check valve. The admitted coolant serves as hydraulic fluid of the cylinder. When the external command to shift the neutron-energy spectrum is entered, the master piston compresses the coolant in the master cylinder. The compressed coolant flows into slave cylinders displacing their slave pistons. The slave pistons carry piston rods which drive rupturing tools into engagement with the tubes rupturing the tubes and admitting the coolant which is a neutron moderator and enhances the moderaton of the neutron energy.

Abstract: A system, for loading a group of elongated rods into a tray from a ramp, which includes a controllable rod stop located on the ramp, an air-tight envelope, and a tray positioning mechanism. The envelope has one end attached to the ramp's lower end and has a hole in its lower surface near the ramp's lower end. The envelope is stiff enough to self-inflate with air and to self-project its opposing end away from the ramp's lower end, when the envelope is left free. The tray positioning mechanism places the tray next to and under the envelope when the rods are to be loaded. When the rod stop is disengaged, the rods roll onto the envelope and are lowered into the tray as the weight of the rods push the air out of the envelope through its hole.

Abstract: Apparatus is disclosed for aligning a laser beam used to perform laser machining operations. The aligning apparatus of this invention is used with laser machining apparatus comprising a laser for emitting a laser beam along a path and a laser lens assembly disposed within the path and movable along an axis for variably focusing the laser beam at a plurality of different focal spots corresponding to the plurality of laser machining operations. The alignment apparatus takes the form of an adjustable mirror, which is disposed to intercept the laser beam and to align at least a portion of the path with the axis of the laser lens assembly, whereby the lateral displacement of each of said plurality of focal spots from the axis is reduced as the laser focusing assembly is moved along its axis.

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 and system for enclosing a gas at a preselected pressure in a nuclear reactor fuel rod having two ends open to its interior. Hermetically enclose each end in a separate airtight chamber. Introduce the gas into the first chamber and open the second chamber to purge the fuel rod interior and both chambers of residual atmosphere. After purging close the open second chamber and determine the gas pressure in the fuel rod interior. When the pressure reaches the preselected value, hermetically seal each fuel rod end while in its respective chamber. After sealing, remove the fuel rod from the chambers.

Abstract: A system for loading nuclear fuel pellets into a sintering boat from a pellet press which discharges newly-made pellets. The loading system includes apparatus for receiving the pellets from the press and inserting them into an upward vertically positioned channel, a horizontally positioned rotatable drum with at least one longitudinally aligned circumferential channel, previously mentioned, for holding a row of pellets, a drum rotating mechanism, a device for pushing the pellets out of a below-horizontally positioned channel, an incline to receive the pushed out pellets, a sintering boat/incline positioner to allow the pellets to leave the incline adjacent the position in the sintering boat of the next-to-be-stacked pellet row, and a controller to coordinate system component operation.

Abstract: A neutron-absorber body for use in burnable poison rods in a nuclear reactor. The body is composed of a matrix of Al.sub.2 O.sub.3 containing B.sub.4 C, the neutron absorber. Areas of high density polycrystalline Al.sub.2 O.sub.3 particles are predominantly encircled by pores in some of which there are B.sub.4 C particles. This body is produced by initially spray drying a slurry of Al.sub.2 O.sub.3 powder to which a binder has been added. The powder of agglomerated spheres of the Al.sub.2 O.sub.3 with the binder are dry mixed with B.sub.4 C powder. The mixed powder is formed into a green body by isostatic pressure and the green body is sintered. The sintered body is processed to form the neutron-absorber body. In this case the B.sub.4 C particles are separate from the spheres resulting from the spray drying instead of being embedded in the sphere.

Abstract: Apparatus for depositing a coating (such as a burnable absorber) on nuclear fuel pellets. Pallets 16 hold a single layer of fuel pellets 22 between lower and upper screened parts 18 and 20. A rotating drum 14 holds the pallets 16 on its circumference. A chamber 12 encloses the drum 14. A sputtering machine 24 has stationary, sputter-frangible, upper and lower targets (such as zirconium diboride) 26 and 28. The stationary upper targets 26 are placed inside the drum's circumference above its longitudinal axis and are pointed facing generally upward and radially outward. The stationary lower targets 28 are placed outside the drum's circumference below its longitudinal axis and are pointed facing generally upward and radially inward. The target material is sputtered onto the fuel pellets 22 as the pallets 16 on the drum 14 rotate past.