Abstract: A method and system for controlling nuclear reactivity in a nuclear reactor are disclosed. The method includes maintaining a nuclear position solution at an initial poison pressure less than the steam pressure within the reactor vessel. The method further includes channeling a pressurizing fluid into the holding tank for pressurizing the poison solution to a pressure greater than the initial pressure thereof, and draining by gravity the poison solution from the holding tank and into the reactor vessel for mixing with the water to reduce reactivity in the core.

Abstract: The present invention is directed to gas-liquid separators especially adapted for the separation of steam exiting the core of a nuclear boiling water reactor that utilizes natural circulation. Such separator has a barrel having a longitudinal axis and width, has an inlet and an outlet, and has a plurality of spaced-apart pickoff rings in fluid communication with annular flow discharge passages. The improved separator of the present invention comprises the pickoff rings having curvilinear shape to direct flow into the flow discharge passages. A twisted strip swirler is positioned along the axis of the barrel after the initial pickoff ring and does not extend the full width of the barrel. The width of the barrel increases at each succeeding pick-off ring from the barrel inlet to the barrel outlet. Advantageously, a low expansion angle exists between the rings and the top of the separator barrel.

Abstract: A spacer for a fuel bundle is disclosed in which a grid type construction provides an approximation to a traditional ferrule spacer. First and second sets of diagonally extending strips of Zircaloy are utilized extending along opposite diagonals across a square sectioned spacer. One set of strips is disposed in a first parallel array along a first diagonal, with each strip of the set being spaced from other strips of the set at rod width spaced intervals along the second and remaining diagonal. The other set of strips is disposed in a second parallel array along an second diagonal, with each strip of the set being spaced from the other strips of the set at rod width spaced intervals along the first diagonal.

Abstract: A hydraulic system for a control rod drive (CRD) includes a variable output-pressure CR pump operable in a charging mode for providing pressurized fluid at a charging pressure, and in a normal mode for providing the pressurized fluid at a purge pressure, less than the charging pressure. Charging and purge lines are disposed in parallel flow between the CRD pump and the CRD. A hydraulic control unit is disposed in flow communication in the charging line and includes a scram accumulator. An isolation valve is provided in the charging line between the CRD pump and the scram accumulator. A controller is operatively connected to the CRD pump and the isolation valve and is effective for opening the isolation valve and operating the CRD pump in a charging mode for charging the scram accumulator, and closing the isolation valve and operating the CRD pump in a normal mode for providing to the CRD through the purge line the pressurized fluid at a purge pressure lower than the charging pressure.

Abstract: A nuclear energy plant housing a boiling water reactor utilizes an isolation condensers with nearly horizontal condenser tubes for both isolation condenser (IC) mode and passive containment cooling system (PCCS) mode, which is entered in response to a loss-of-coolant accident (LOCA). These tubes extend between a cylindrical distributor and a cylindrical collector. In either mode, the reactor vessel is coupled to the cylindrical distributor. Steam reaching the condenser is condensed to water, which flows back to the vessel, providing a cooling effect. In PCCS mode, gas exiting the tubes is trapped and diverted into a wet well. This diversion path is not avialable in IC mode. As a result water exits the tubes more slowly in IC modes in PCCS mode. The water remaining in the tubes during IC mode renders the condenser less efficient. This lower efficiency partially offsets the greater heat exchange in IC mode due to higher temperature differentials and the relatively absence of noncondensable gases.

Abstract: A recirculation system is disclosed for driving reactor coolant water contained in an annular downcomer defined between a reactor vessel and a reactor core spaced radially inwardly therefrom. The system includes a plurality of circumferentially spaced pumps disposed in the downcomer, each pump including an inlet for receiving coolant water from the downcomer as pump inlet flow, and an outlet for discharging the pressurized water. The recirculation system firstly increases the pressure of the pump inlet flow at the pump inlet before being sucked into the pump for being further pressurized by the pump.

Abstract: A drive for positioning a control rod in a nuclear reactor core is disclosed. The drive includes a housing having a piston disposed therein, with a piston rod extending from the piston and through the housing for being joinable to the control rod. A driving fluid is provided into the housing for exerting a pressure force against the piston for moving the piston and the control rod. The output requirements for the driving fluid are varied in response to the position of the piston for selectively controlling intermediate positions of the piston.

Abstract: A boiling water nuclear water plant includes a reactor core isolation cooling (RCIC) system in which a turbine used to pump feedwater to the reactor also drives a generator. The generator is used to drive RCIC components, such as a room cooler and control electronics, during station blackout.

Abstract: A forced-circulation boiling-water reactor includes bypass check valves between a downcomer and a core inlet plenum. When the recirculation pumps are operating at full capacity, there is a maximum pressure differential from the downcomer to the core inlet plenum. This pressure differential keeps the valves closed so that recirculating fluid is constrained to flow through the pumps. When the pumps are not operating, a driving water head in the downcomer forces the valves open, augmenting the flow cross section between the downcomer and the core inlet plenum, enhancing natural circulation. The enhanced natural circulation provides greater core stability during pump shutdown. The valves are selected or adjusted so that they open when the pressure differential falls through a predetermined range to augment diminished pumping capacity with a higher natural circulation flow rate.

Abstract: A method for tack welding a clip same to a support surface to removably secure a cable and instrumentation which may be connected on the cable in an environment wherein fluid flow is imposing loadings such as vibrations on the support surface, the environments of use including nuclear reactors, wind tunnels and the like. The restraint clip can comprise a single-piece body having a loop part wrapped around the cable and a pair of generally flat anchor plates extending codirectionally in juxtaposed relationship away from opposite ends of the loop part, the clip being fixed to the support surface by tack welding the two anchor plates to each other, and one of the anchor plates to the support surface. Removal of the clip from its fixing to the support surface preferably is effected with prying force applied to the loop part from behind the loop part with a tool anchored against the support surface.

Abstract: An improved apparatus and method for ultrasonic inspection of materials through barriers such as gaps in manufactured parts is disclosed. The improvement herein is directed to enabling such ultrasonic testing to bridge ambient gaps such as intentionally formed gaps in composite structures having a first structure for originally receiving and transmitting sound separated by the gap from another structure to be inspected. Preferably, the gap is flooded with a gas having a predictable and optimum speed of sound relative to the material of the first and second structures. Sound is propagated to the first structure in a wave packet that is transmitted through the couplant fluid. The sound is generated in a wave packet having a spatial width at least twice the dimension of the gap to be bridged. The wave packet has a contained frequency having a wavelength (relative to the speed of sound of the gas flooding the gap) to create a constructively interfering standing wave node within the gap.

Abstract: A reactor core includes upper and lower matrices of fuel bundles. Fuel rods in the upper matrix have their plenums oriented upward, while fuel rods in the lower matrix have their plenums oriented downward. Refueling involves removal of a first bundle in the upper matrix, removal and retirement of the bundle in the lower matrix directly below the original position of the first bundle, inversion and installation of the first bundle in the lower matrix, and installlation of a new bundle in the upper matrix. The new bundle is installed plenum-side up. The bi-level core provides greater flexibility in repositioning fuel bundles for longer burnups and lower high-level waste. In particular, problems with axial spectral variations in neutron flux can be compensated using the disclosed core arrangement and refueling procedure.

Abstract: An apparatus and method to facilitate the in situ detection of small leaks in fluid-filled, capacitive type pressure transducers by remotely and non-intrusively inducing a brief time varying transient signal, and then analyzing the frequency response of the transducer to such excitation in order to detect the presence and effects of a fluid leak. The adverse effect of this induced transient signal on the process control circuitry is insignificant, while providing for an accurate and sensitive method for detecting the extent of fluid loss in the transducer when evaluated according to the present invention. As a consequence of such transducer evaluation techniques, frequency responsive characteristics of such devices may be recorded and self-correlated over long periods of time.

Abstract: Disclosed is a device for measuring dimensional characteristics of an elongate component which comprises:(a) an elongate rigid support that bears (i) an upper platform upon which is mounted a drive; (ii) a clamp mechanism for securing said component about its proximal end in a reference position; (iii) a lower platform which supports a pedestal for securing said component about its distal end in a reference position; and(b) a sensor carriage movably mounted to said rigid support and operatively connected to said drive for movement along the elongate extent of said support and having an opening penetrating therethrough for receiving said elongate component when it is secured by and substantially parallel to said rigid support, said carrier bearing a plurality of pivotally-mounted bell cranks spaced about said opening, each bell crank having a wheel for riding on said component during movement of the carrier and being in contact with a sensor capable of providing a signal correlative to displacement of the bell

Abstract: A drive for positioning a control rod in a nuclear reactor core is disclosed. The drive includes a turbine rotor joined to a hollow spindle in a housing. The spindle has a piston disposed therein and a piston rod extending therefrom and through a bottom end of the spindle for being joined to the control rod. A pressurized fluid is provided into the spindle for exerting a pressure force against the piston for moving the piston for selectively gripping the control rod. Interruption of the pressurized fluid to the spindle causes ungripping of the control rod.

Abstract: Nuclear fuel cladding tube end plug welds are ultrasonically scanned to develop data indicative of weld thickness, weld penetration, and the existence and size of any included feature, such as pores. A computer analyzes the data to determine critical weld characteristics which are then tested against established quality assurance standards to see if the end plug weld is acceptable, all on an automated production line basis.

Abstract: A steam separator for a boiling water reactor includes a pressure vessel and a chimney spaced radiallly inwardly therefrom to define a downcomer therebetween for recirculating water, the chimney being disposed above a reactor core for channeling upwardly therefrom steam voids and water flow. An annular partition wall is spaced radially between the vessel and he chimney to define an annular collection chamber having an inlet for receiving a portion of the steam voids and water flow from the chimney, a steam outlet for discharging the steam voids from the chamber, and a flow outlet for discharging the water flow from the chamber into the downcomer.

Abstract: A fuel handling system for nuclear reactor plants comprising an improved underwater grapple means for transferring fuel units while submerged within a water containing reactor vessel. Wherein a novel structure is provided which allows for direct viewing downward for operating the grapple hooks.

Abstract: A radial brake assembly is disclosed for selectively preventing rotation of a shaft, such as a shaft used in a control rod drive for a nuclear reactor. The brake assembly includes a stationary housing, a rotor disc fixedly connected to the shaft for rotation therewith, and a brake member disposed adjacent to the perimeter of the rotor disc. The rotor disc includes at least one rotor tooth and the brake member includes at least one braking tooth. The brake member is selectively positioned in a deployed position for allowing the braking tooth to contact the rotor tooth for preventing rotation of the shaft in a first direction, and in a retracted position for allowing the rotor disc and shaft to rotate without restraint from the brake member.

Abstract: In a boiling water nuclear reactor having its core, fuel support casting, and control rod guide tubes removed to expose the core plate, a method for the submerged welding repair and replacement of the control rod drive housing at the bottom extremity of the reactor vessel is disclosed. An alignment device registers to a hole in the core plate and its corresponding guide pin. A control rod drive housing mating fixture on the depending extremity of the shaft of the alignment device precisely fits and mates to the top of the control rod drive housing. The alignment device includes cross electronic levels sealed for submersion which levels remotely transfer through attached wiring the precise angularity between the top of the control rod drive housing on one hand and the corresponding and overlying hole in the core plate on the other hand. For the welding repair process herein, a welding cylinder apparatus fits over the depending end of the shaft of the alignment device.