Abstract: Damper systems selectively reduce coolant fluid flow in nuclear reactor passive cooling systems, including related RVACS. Systems include a damper that blocks the flow in a coolant conduit and is moveable to open, closed, and intermediate positions. The damper blocks the coolant flow when closed to prevent heat loss, vibration, and development of large temperature gradients, and the damper passively opens, to allow full coolant flow, at failure and in transient scenarios. The damper may be moveable by an attachment extending into the coolant channel that holds the damper in a closed position. When a transient occurs, the resulting loss of power and/or overheat causes the attachment to stop holding the damper, which may be driven by gravity, pressure, a spring, or other passive structure into the open position for full coolant flow. A power source and temperature-dependent switch may detect and stop holding the damper closed in such scenarios.

Abstract: Control rod drives include all-digital monitoring, powering, and controlling systems for operating the drives. Each controlling system includes distinct microprocessor-driven channels that independently monitor and handle control rod drive position information reported from multiple position sensors per drive. Controlling systems function as rod control and information systems with top-level hardware interfaced with nuclear plant operators other plant systems. The top-level hardware can receive operator instructions and report control rod position, as well as report errors detected using redundant data from the multiple sensors. Positional data received from each drive is multiplexed across plural, redundant channels to allow verification of the system using independent position data as well as operation of the system should a single channel or detector fail.

Abstract: Control rod drives include linearly-moveable control elements inside an isolation barrier. Control rod drives move the control element through secured magnetic elements subject to magnetic fields. Induction coils may generate the magnetic fields across a full stroke length of the control element in the reactor. A closed coolant loop may cool the induction coils, which may be in a vacuum outside the isolation barrier. A control rod assembly may house the magnetic elements and directly, removably join to the control element. The control rod assembly may lock with magnetic overtravel latches inside the isolation barrier to maintain an overtravel position. Overtravel release coils outside the isolation barrier may release the latches to leave the overtravel position. Methods of operation include selectively energizing or de-energizing induction coils to drive the control element to desired insertion points, including full insertion by gravity following de-energization.

Abstract: Control rod drives include linearly-moveable control elements inside an isolation barrier. Control rod drives move the control element through secured magnetic elements subject to magnetic fields. Induction coils may generate magnetic fields and be moveable across a full stroke length of the control element in the reactor. A motor may spin a linear screw to move the induction coils on a vertical travel nut. A control rod assembly may house the magnetic elements and directly, removably join to the control element. The control rod assembly may lock with magnetic overtravel latches inside the isolation barrier to maintain an overtravel position. Overtravel release coils outside the isolation barrier may release the latches to leave the overtravel position. Operation includes moving the induction coils with a linear screw to drive the control element to desired insertion points, including full insertion by gravity following de-energization. No direct connection may penetrate the isolation barrier.

Abstract: A method of cleaning a jet pump assembly of a nuclear reactor may comprise inserting a cleaning tool into the jet pump assembly such that a front face of the cleaning tool is adjacent to an inner surface of the jet pump assembly and below a level of a first liquid in the jet pump assembly. The method may additionally comprise directing a plurality of front jets of a second liquid from a plurality of front orifices on the front face of the cleaning tool such that the plurality of front jets of the second liquid strikes the inner surface of the jet pump assembly. The method may further comprise maintaining a standoff distance between the front face of the cleaning tool and the inner surface of the jet pump assembly during the cleaning of the jet pump assembly.

Abstract: Nuclear reactors include isolation condenser systems that can be selectively connected with the reactor to provide desired cooling and pressure relief. Isolation condensers are immersed in a separate chamber holding coolant to which the condenser can transfer heat from the nuclear reactor. The chamber may selectively connect to an adjacent coolant reservoir for multiple isolation condensers. A check valve may permit coolant to flow only from the reservoir to the isolation condenser. A passive switch can operate the check valve and other isolating components. Isolation condensers can be activated by opening an inlet and outlet to/from the reactor for coolant flow. Fluidic controls and/or a pressure pulse transmitter may monitor reactor conditions and selectively activate individual isolation condensers by opening such flows. Isolation condenser systems may be positioned outside of containment in an underground silo with the containment, which may not have any other coolant source.

Abstract: Chimneys include several combinable parts useable in nuclear reactors. The parts are modular and removably joinable without destruction for use in directing flow in an operating nuclear reactor and directly fit in storage area during non-operation. Chimney parts are joinable through flanges and connecting structures. Chimney parts may include partitions that divide or direct energetic coolant flow from a nuclear core as well as steam separating and drying structures. The parts each individually fit within storage areas of the nuclear plant, including equipment or buffer pools in the refueling floor of the plant. Methods move the chimney parts between the reactor and storage areas, and multiple parts may be stacked or nested in such moves. Methods are useable underwater and with storage pools to prevent exposure of chimney parts during an outage. During operation, chimneys are useable in place of existing single-piece chimneys.

Abstract: A system for measuring a level of a liquid may include a receptacle, a probe, a pulsing unit, and a digitizer. The receptacle has a top and a bottom and is configured to contain the liquid. The probe may extend into the receptacle through the bottom. The pulsing unit is configured to transmit a pulse to the probe. The digitizer is configured to receive at least a first reflected pulse and a second reflected pulse from the probe. The time between the first reflected pulse and the second reflected pulse may be calculated and converted to a distance that is indicative of the level of the liquid in the receptacle.

Abstract: A steam separation system includes a standpipe configured to receive a gas-liquid two-phase flow stream and a diffuser configured to receive the gas-liquid two-phase flow stream from the standpipe. The diffuser includes a swirler configured to separate the gas-liquid two-phase flow stream. The swirler includes a plurality of swirler vanes and a straightener structure. The straightener structure includes a hub. The plurality of swirler vanes is mounted radially around the hub, and a straightener extends in an upward direction from the hub. The system also includes a separation barrel configured to receive the gas-liquid two-phase flow stream from the swirler. The separation barrel includes a rifled channel having orifices along an inner surface thereof. The plurality of swirler vanes is tuned with the rifled channel, such that an angle of each of the plurality of vanes corresponds to an angle of the rifled channel.

Abstract: A combined blade guide and exchange tool, include a blade guide tool having a lower end and an upper end and a plurality of frame rails supporting a pair of lower collet housings at a lower end of the blade guide tool. A pair of fuel support grapple actuating rods are supported between the plurality of frame rails and have a first end engaging a pair of collets within the pair of lower collet housings and a second end disposed at the upper end of the blade guide tool. A blade exchange tool is releasably mounted to the upper end of the blade guide tool and includes a pair of upper collets for engaging the pair of fuel support grapple actuating rods. The blade exchange tool further including a slider and hook assembly attached to a cable guided by the blade exchange tool and adapted for engaging a control rod.

Abstract: A remotely operated vehicle (ROV) for inspecting a core shroud having an outer surface may include: a body configured to be operatively connected to a tether; and/or a sensor, configured to be operatively connected to the body, and configured to provide inspection information of the shroud. The tether may be configured to provide vertical position information for the ROV relative to the outer surface. A system for inspecting a core shroud may include: a trolley; an arm; the tether; and/or the ROV. The arm may be configured to be operatively connected to the trolley. The ROV may be configured to be operatively connected to the arm via the tether. A method for inspecting a core shroud may include: installing a system for inspecting the shroud on the shroud; driving the system horizontally around the shroud; and/or using a sensor of the system to inspect the shroud.

Abstract: A feedwater sparger repair assembly includes a cover plate having a partial cylindrical shape and having a nozzle opening and a pair of bolt openings extending through the cover plate. A nozzle is attached to the cover plate and surrounds the nozzle opening. A pair of T-bolts extend through a respective one of the pair of bolt openings and each include a shank having a threaded portion extending from an exterior side of the cover plate and a partial cylindrical head portion disposed at an end of the shank on an interior side of the cover plate. A pair of nuts are engaged with the threaded portion of the pair of T-bolts. The feedwater sparger repair assembly is adapted to be mounted to an opening that is cut into a core spray pipe in order to repair/replace a sparger that becomes cracked.

Abstract: A method and apparatus of limiting power of a boiling water nuclear reactor system includes a reactor pressure vessel, a reactor core disposed in the reactor pressure vessel, a core shroud surrounding the reactor core, a downcomer region disposed between an inner surface of the reactor pressure vessel and the core shroud, a steam line connected to an upper end of the reactor pressure vessel and a condenser system that receives steam from the reactor pressure vessel. A portion of the condenser system condensate is returned to the reactor pressure vessel of the boiling water reactor inside the core barrel above the core rather than into the downcomer. Returning the condensate in this way increases the effectiveness of an isolation condenser system or if the condensate is a portion of the feedwater from the main condenser it provides an effective means to regulate core flow and core power.

Abstract: A pump leakage mitigation device includes one or more clamp arms on an outer surface of a pump that can be driven by a biasing element to seat against a shaft of the pump to seal or reduce fluid flow through a breakdown of the pump. The biasing element engages only at threshold temperatures, such as those associated with breakdown orifice failure when additional sealing may be necessary. Clamp arms of any number and shape can be used to achieve the desired seal and based on the pump geometry. A sealant surface and/or keeping mechanism are useable with the leakage mitigation device to enhance fluid flow blockage throughout a pump failure transient scenario. Pump leakage mitigation devices are installed on an outside of a variety of different pump types and can thus be installed, actuated, manipulated, disengaged, and/or removed without having to destroy or disassemble the pump.

Abstract: Control rod drives include linearly-moveable control elements inside an isolation barrier. Control rod drives move the control element through a motor and rotor powering a linear screw internal to an isolation barrier. Induction coils may generate magnetic fields and be moveable across a full stroke length of the control element in the reactor. The magnetic fields hold closed a releasable latch to disconnect the control elements from the linear drives. A control rod assembly may join to the control element. The control rod assembly may lock with magnetic overtravel latches inside the isolation barrier to maintain an overtravel position. Overtravel release coils outside the isolation barrier may release the latches to leave the overtravel position. Operation includes moving the magnetic fields and releasable latch together on opposite sides of an isolation barrier to drive the control element to desired insertion points, including full insertion by gravity following de-energization.

Abstract: Mobile apparatuses move within contaminated fluid to create fluid flows against structures that remove and prevent contaminant deposition on structure surfaces immersed in the fluid. Unsettling flows in water may exceed approximately 2 m/s for radionuclide particles and solutes found in nuclear power plants. Mobile apparatuses include pressurized liquid from a pump or pressurized source that can be chemically and thermally treated to maximize deposition removal. When spraying the pressurized liquid to create the deposition-removing flow, mobile apparatuses may be self-propelled within the fluid about an entire surface to be cleaned. Mobile apparatuses include filters keyed to remove the contaminants moved into the coolant by the flow, and by taking in ambient fluid, enable such filtering of the ambient fluid along with a larger flow volume and propulsion. Propulsion and the pressurized liquid in turn enhance intake of ambient fluid.

Abstract: A PCCS condenser may include a first and a second stage condenser. Each of the first and second stage condensers may include channels in fluid communication between an inlet and an outlet header. The inlet header of the first stage condenser may be configured to receive a fluid mixture through a first inlet opening. The channels may be configured to condense water from the fluid mixture flowing through the channels from the inlet header to the outlet header, respectively, of the first and second stage condenser. The PCCS condenser may include a catalyst in at least one of the outlet header of the first stage condenser or the inlet header of the second stage condenser. The catalyst may catalyze a reaction for forming water from hydrogen and oxygen in the fluid mixture. The outlet header of the second stage condenser may be in fluid communication with a combined vent-and-drain line.

Abstract: An apparatus configured to structurally replace a cracked weld in a nuclear plant may include: a first body portion that includes a first gripping portion; a second body portion that includes a second gripping portion; a wedge portion between the first and second body portions; and/or an adjustment portion. The first body portion may be configured to slidably engage the second body portion. The wedge portion may be configured to exert force on the slidably engaged first and second body portions. The adjustment portion may be configured to increase or decrease the force exerted by the wedge portion on the slidably engaged first and second body portions. When the adjustment portion increases the force exerted by the wedge portion on the slidably engaged first and second body portions, a distance between the first and second gripping portions may decrease.

Abstract: A method of facilitating modeling of a system includes receiving, at a processor, an extensible markup language (XML) file corresponding to a piping and instrumentation diagram (PID) of the system; identifying, by the processor, components of the system that are described in the XML file, the XML file including information about attributes of the identified components; storing, by the processor, the information about the attributes of the identified components; and generating, by the processor, a simulation model page using syntax of a simulation modeling software environment, based on the stored information about the attributes of the identified components.

Abstract: Slip joint clamps seat on a diffuser end via external features of the diffuser, like guide ears, regardless of slip joint wear or damage. The clamps can be opened and closed to surround an inlet mixer forming a slip joint with the diffuser without disassembly. Slip joint clamps drive or bias the inlet mixer in a lateral direction largely perpendicular to the axial orientation and end of the diffuser to achieve a desired preload force in the inlet mixer and clamp connection. Clamp arms include rotatable halves that, when joined, form a complete fill between an inner surface of the diffuser and outer surface of the inlet mixer. A lateral drive pushes the inlet mixer against the clamp and may include a resistive element. An accessible set of guide ear bolts and lateral driving bolts permit exterior manipulation to axially mount or laterally bias the clamp in the slip joint.