Abstract: A means for damping a low-friction azimuth resolver by use of an array of small magnets acting on a metallic pendulum attached to the resolver shaft. The magnetic field acts on the pendulum motion to induce a motional electromotive force and associated currents, which produce forces opposed to the motion, thereby acting as a non-contact damper on the resolver shaft. When the resolver shaft is at rest, no "eddy currents" are produced in the static magnetic field and no damping force exists. If the shaft moves, the attached pendulum cuts the magnetic flux lines and produces a drag force proportional to the shaft angular speed. The pendulum is typically made of diamagnetic material, such as lead or copper, thereby assuring that the induced forces arise solely from the motion. The magnetic field is produced by an array of small, but intense, samarium-cobalt magnets contained in a compact package providing for uniform damping throughout 360.degree. of resolver motion.

Abstract: A durable coating process which provides improved adhesive bond strength between the coating and its substrate. This process utilizes spray parameters which generate a unique plasma coating that can be applied through a liquid environment between the spray gun nozzle and the substrate to provide combined ion cleaning, etching and activation of the surface to be coated. The improved surface conditioning allows the creation of an exceptionally strong metallurgical bond at the interface between the splattered droplets of the coating material and the substrate. The improved plasma coating process utilizes a relatively short nozzle-to-work surface distance and is therefore suitable for use directly in a liquid such as water in order to keep the substrate from overheating, which may be more likely to occur if the coating were applied in a gas or vacuum environment.

Abstract: A method of arc voltage sensing and electrode position control during mechanized electric arc welding. This welding method utilizes a lower power mode of the arc which has an improved voltage sensing geometry, and allows welds to be reliably made between components having small weld joint widths. The arc voltage is sensed only during the lower power mode. The sensing step is performed at a sensing time which is delayed relative to the start of said low power period, the duration of the delay being sufficient to allow the weld pool produced during the high power period to partially solidify. This method improves the voltage stability and arc position of the welding process, preventing the problem of the arc "climbing" the side walls of the weld groove. During the low-power arc voltage sensing mode, the arc is narrower and therefore more focused on the preferred bead center sensing position of a weld pass rather than spread out onto the adjacent side walls.

Abstract: A joint for interfacing a steel head closure and a steel-lined prestressed concrete reactor vessel (PCRV). The steel head closure is bolted to a thick steel annular plate and a thermal barrier is arranged in a volume bounded by the head ring, the liner and the concrete of the PCRV wall. The thermal barrier is made of zirconia sand or other material having a low thermal conductivity, a high bulk modulus equal to that of concrete, and a low shear modulus. Differential thermal expansion of the vessel head closure and PCRV is accommodated by a flexible connection of the PCRV liner to the inner periphery of the head ring. In the alternative, the steel head closure is interfaced to the top of the PCRV via a sliding joint or a thermal stress relief ring. In accordance with a further alternative, thermal stresses in the steel vessel head closure are mitigated by reducing the temperature of the head closure by installing thermal insulation on all internal surfaces thereof.

Abstract: A remotely installable piping support attachment employs a T-bolt type of blind fastener for clamping a relatively smaller instrumentation pipe, e.g., the jet pump sensing line, to the wall of an adjacent structure, e.g., the inlet mixer diffuser. The attachment assembly includes a T-bolt, a split pipe clamp support, a ratchet nut with peripheral ratchet teeth, and a ratchet lock washer. The head of the T-bolt is inserted through an elongated hole machined in the diffuser wall and then rotated so that the T-bolt head cannot pass back through the elongated hole. When the nut is tightened on the threaded shank of the T-bolt, a top plate and an anchor of the split pipe clamp support are pressed together to clamp the jet pump sensing line therebetween. The ratchet lock washer is counterbored for receiving the nut and slotted to provide an integral spring arm encircling the nut.

Abstract: An apparatus for stabilizing a shroud against vertical and lateral deflection. The apparatus forms a vertical load path by which the shroud flange can be anchored to the shroud support plate. In the tensioned state, an upper support assembly exerts a restraining force on the top surface of the shroud flange which opposes separation of the shroud at any assumed failed circumferential weld location. The apparatus further incorporates upper and lower restraint springs which oppose lateral deflection at the elevation of the top guide support ring and at the elevation of the core plate support ring respectively. The vertical restraint assembly is made of material having a coefficient of thermal expansion which is less than a coefficient of thermal expansion of the shroud material. A desired differential thermal expansion of the vertical restraint assembly and the shroud can be attained by the selection of member lengths and materials having appropriate coefficients of thermal expansion.

Abstract: An apparatus for cleaning of a reactor pressure vessel head closure stud. The surface of the stud is cleaned by power vacuum brushing. The stud is hung vertically in a cabinet which supports a vertically elevatable spinner housing. The stud is cleaned in a single process using a rotating wire brush system which is rotatably mounted in the spinner housing and has a central opening for passage of the stud. A plurality of wire bushes are arranged in a circular array surrounding the stud. While the wire brushes are rotating in contact with the stud external surface, the spinner housing and wire brush assembly are displaced vertically by an elevator so that the rotating brushes travel along the full length of the stud. The rotating brushes remove accumulated material on the stud surface. The resulting contaminated debris is contained in a volume enclosed by a brush canister and a bellows. The bellows expands or contracts as the elevator travels.

Abstract: An apparatus for repairing the core shroud of a nuclear reactor having one or more cracked vertical seam welds. The repair involves installation of a ring around the circumference of the shroud while the reactor is shutdown. The ring is tensioned with a mechanical preload and then vertically supported with shear bolts or struts. The ring is made of an alloy having a coefficient of thermal expansion less than the coefficient of thermal expansion of the shroud material. When the reactor returns to operation, the consequent temperature rise causes the shroud to expand more than the ring expands. As a result the ring exerts a circumferential compressive load across any cracks in the vertical seam welds intersected by the ring.

Abstract: A system for ensuring the distribution of noble metal in the reactor circuit during plant application without measuring the reactor water for noble metal content by chemical analysis. The system performs the measurement of electrochemical corrosion potential in an autoclave or a high-flow test section that is connected to the reactor water circuit through sample lines downstream of the injection port, preferably the point in the reactor circuit which is furthest from the injection port. If the noble metal flows into the autoclave or test section at these distant points in the reactor circuit, then the noble metal will deposit on the test specimens inside the autoclave or test section.

Abstract: A multiple-filler-material guide nozzle assembly for feeding multiple fusible filler metal wire or other metal forms into reduced-width, high-aspect-ratio (ratio of depth to width) metallic joints with control and stability of the filler metal position as it enters the molten pool area. The multiple filler materials are fed concurrently at the same or different feed rates. To control the aiming consistency for each of the multiple fillers even with substantial amounts of "cast" in the filler shape (after being unwound from a spool), the nozzle holes can be curved to match the curvature of the "cast" filler wire. This forces the curved filler wire to consistently follow the predetermined orientation of the curved shape of the nozzle. The multiple nozzles can be used to compensate for weld dilution effects by alloying to generate more favorable uniform, gradient or stepped compositions in joints or cladding.

Abstract: An integrated apparatus for inspecting the arms of jet pump beams using eddy current technology, while also scanning the borehole region using ultrasound technology. In order to inspect the jet pump beam arms, a special scanner is required to properly move an eddy current coil in two dimensions over the complex machined surface on top of the arms. The scanner has two axes of motion and can perform a raster scan in either direction. The inspection payload, an eddy current probe, moves the length of the scanning axis and then the payload is indexed (i.e., moved a small distance) along the indexing axis. The payload is then moved smoothly back along the length of the scanning axis. Data is collected only during motion along the scanning axis. The scanner has a unique curved track design for maintaining the orientation of the eddy current probe perpendicular to the inspection surface. It allows inspecting the top flat surface and the curved edges of the jet pump beams.

Abstract: A tool for vertically supporting a shroud repair tie rod assembly having a clevis hook by bracing the clevis hook against a clevis pin installed in a gusset plate. This allows the vertical support at the upper end of the tie rod assembly to be removed, so that the upper support structure can be coupled to the tie rod. The lower end of the tie rod assembly is supported on both sides of the gusset plate. The tool for vertically supporting the lower end of the tie rod assembly is designed to fit in the narrow space bounded by a jet pump diffuser, the gusset plate and the reactor pressure vessel. The vertical support tool includes a pole adaptor for coupling to the end of a service pole, a pole adaptor extension having one end connected to the pole adaptor, a mounting block connected to the other end of the pole adaptor extension, and a hydraulic spreader mounted on the mounting block. The hydraulic spreader opens in response to actuation of a hydraulic cylinder.

Abstract: A nut runner tool is used to engage, turn, capture and lift the RPV head closure nuts from the RPV studs. The tool is also used to capture, lift and transport the nuts from the storage tray to the RPV head closure studs. The nut runner system enables a single operator to remove and install head closure nuts quickly and safely. The nut runner is powered by a remotely operated air driver. The reaction torque is transferred safely through the tool into the top of the closure stud. The air driver unthreads the nut, then a nut holding device is actuated, and the nut and tool are lifted from the top of the stud with a hoist attached to a trolley. The nut and tool are moved radially from the stud location to the storage position in the nut rack. When positioned over the storage location, the lowering of the nut into the rack is performed by the hoist, eliminating the need to manhandle the nuts into and out of the storage rack.

Abstract: A tool for installing and torquing a tensioning nut onto a tie rod of a shroud repair apparatus. The nut torquing tool has a socket for coupling with the tensioning nut and an adaptor for coupling with a manually operated handling pole, wherein the axis of rotation of the socket is radially displaced relative to the axis of rotation of the adaptor. The respective shafts connected to the socket and adaptor are coupled by means of a pair of sprockets and a chain which convert rotation of the adaptor into rotation of the socket. The distance between the sprockets can be adjusted to tension the chain. The handling pole adaptor is connected to a drive shaft by way of a universal joint, a torque limiter and a torque multiplier. Incorporation of a torque multiplier facilitates installation and torquing of the tensioning nut in a single operation using a lightweight handling pole.

Abstract: A process for providing a significant improvement in the detrimental tensile residual stress condition on the root side of welds, especially on the inside wall of piping welds. The method uses a high welding torch travel speed (>10 inches/min), especially on the last one or two cap passes. The process relies on the limited thermal heat sink capability of the pipe wall and nearly completed weld joint itself to generate a significant through-wall temperature gradient, and therefore a sufficient through-wall stress gradient during the welding. This stress gradient results in metal plasticity and permanent strains, and therefore a reduction in the magnitude of the final residual stress or, preferably as conditions allow, a reversal in the direction of the stresses from tensile to compressive. The method can be used as a welding process or as a heat treatment. In the case of heat treatment, the far surface of the weld joint is heated without fusion of the material making up the far surface.

Abstract: A self-cleaning, self-propelled strainer designed for installation in boiling water reactor suppression pools. The strainer is designed to prevent strainer clogging and subsequent loss of the emergency core cooling system flow during a postulated design basis loss-of-coolant accident. This self-cleaning strainer is driven by a turbine placed in the strainer flow path. The turbine drives rotation of a brush-and-plow arrangement. The wiping action of the brush and the centrifuging action of the plow remove insulation debris and other particulate matter which might be generated by the LOCA, thereby preventing the strainer from plugging.

Abstract: Spring latching mechanisms for preventing relative rotation or relative displacement of assembled components during operation of a nuclear reactor. The first type of mechanism prevents rotation of a threaded fastener which fastens a first component to a second component. The fastener has a multiplicity of longitudinal recesses formed on an outer circumferential surface thereof. The spring latching mechanism has a cantilever beam supported at one end by the first component. The other end of the cantilever beam is displaceable between first and second positions as the cantilever beam flexes. An interlocking member connected to the second end of the cantilever beam fits engages one of the longitudinal recesses in the fastener, whereby rotation of the fastener can be blocked. The second type of mechanism positively locates and prevents vibration-induced wear of first and second components assembled with play therebetween.

Abstract: An apparatus for carrying out a surveillance program to monitor the neutron fluence and its effect on vessel materials at a position in the annular space between the pressure vessel and core shroud of a boiling water reactor for the purpose of monitoring vessel embrittlement. The apparatus includes an offset capsule holder assembly which fits in an existing capsule holder attached to the inner surface of the pressure vessel wall. The offset capsule holder assembly positions a new capsule holder radially closer to the core, by an amount determined by neutron transport calculations. The new capsule holder is geometrically identical to the original, or a "replacement in kind", allowing the original surveillance capsules to be immediately reinstalled. With the water moderator in the downcomer annulus, the fluence rate increases significantly when the surveillance capsule is moved radially inward from the pressure vessel inside surface toward the core.

Abstract: A method for determining the core flow rate from pump differential pressure method equations and a heat balance equation for determining the temperature and density of the reactor water in the downcomer and lower plenum region. The measured reactor water temperature is used only as an initial estimate for this new method. This allows the first estimate of the core flow to be determined based upon the reactor water density that corresponds to this temperature and the pump differential pressure and pump rotational speed measurements. Then, with this intial core flow measurement value, and other available plant measurements and assumed nominal values for the heat balance equation, revised values for the reactor water temperature and density can be calculated. Using a standard numerical method, such as the successive approximation technique, a more accurate estimate for the reactor water density can be obtained.

Abstract: A tool for vertically supporting a shroud repair tie rod assembly having a clevis hook by bracing the clevis hook against a clevis pin incorporated on a lower support fixture toggle-bolted to the shroud support plate. The provision of vertical support at the bottom of the tie rod assembly allows the vertical support at the top of the tie rod assembly to be removed, so that the upper support structure can be coupled to the threaded upper end of the tie rod. The lower end of the tie rod assembly is supported on both sides of a vertical support plate of the fixture. The tool for vertically supporting the lower end of the tie rod assembly comprises a support frame which sits on the top surface of a fixture bracket while receiving the coupled toggle bolt and nut in a recess that allows the tool to rotate about the axis of the toggle bolt.