Abstract: There is provided a gear device including an input shaft to which power is input, an internal gear, and an external gear. The input shaft has an input shaft hollow portion that extends in an axial direction, and an internal gear portion that meshes with an input pinion to be rotationally driven. The internal gear portion is configured so that the input pinion internally meshing with the internal gear portion and the input shaft hollow portion do not overlap each other when viewed in the axial direction.

Abstract: The drive assembly includes annular drive magnets extending around a top end of a drive shaft and annular drive coils extending around the drive magnets, separated by a pressure boundary. A latch assembly is coupled to the drive magnets and engages with the drive shaft in response to actuation of the drive assembly. The drive coils also rotate the drive magnets and the engaged latch assembly to axially displace the drive shaft. Deactivating the drive coils disengages the latch assembly from the drive shaft, dropping a connected control rod assembly via gravity into a nuclear fuel assembly.

Abstract: Provided is an installation structure for installing control rod drive mechanisms and cable sealing units in a nuclear reactor pressure vessel. The installation structure includes: a sealing flange having a ring shape and being hermetically coupled to an upper pressure vessel and a lower pressure vessel of the nuclear reactor pressure vessel; a cylindrical tube extending downward vertically from an internal edge of the sealing flange; and a support plate provided horizontally to block a lower end portion of the cylindrical tube. A plurality of mounting holes that penetrate through the sealing flange horizontally are arranged in the sealing flange with a predetermined interval therebetween along a circumferential direction, the cable sealing units are inserted and mounted in the plurality of mounting holes, and the control rod drive mechanisms are installed on the support plate to be supported.

Abstract: This variable electric motor system includes an electrically powered device (50) and a planet gear transmission device (10). One of a sun gear shaft (12), a planet gear carrier shaft (27), and an internal gear carrier shaft (37) of the planet gear transmission device constitutes an output shaft (Ao), another shaft constitutes a constant-speed input shaft (Ac), and another shaft constitutes a variable-speed input shaft (Av). The electrically powered device includes: a constant-speed electric motor (51) including a constant-speed rotor (52) that rotates about the axis (Ar), and connected to the constant-speed input shaft; and a variable-speed electric motor (71) including a variable-speed rotor (72) that rotates about the axis, and connected to the variable-speed input shaft. The variable-speed rotor has a shaft insertion hole (74) formed in the axial direction, the hole having a cylindrical shape centered on the axis. The constant-speed rotor is inserted through the hole.

Abstract: A magnetostrictive wire control rod position indicator for determining a real-time position of a control rod using a mutual interference effect between a magnetic field formed by supplying a pulse current to a magnetostrictive wire provided inside a protecting tube and a magnetic field formed by a permanent magnet of a drive shaft includes magnet members installed at an upper limit position and a lower limit position of the magnetostrictive wire control rod position indicator to cause magnetic field interference with the permanent magnet of the drive shaft.

Abstract: A control rod drive mechanism includes an outer tube and a guide tube which is arranged in the outer tube and is held by the outer tube. Furthermore, the control rod drive mechanism includes a spool piece with an inner magnet coupling and a rotary shaft connected to the inner magnet coupling arranged internally. The lower end portion of the outer tube is supported by the spool piece in the spool piece. The outside diameter of the outer tube, through the length of the outer tube, is smaller than the inside diameter of the spool piece and the outer tube, in the radial direction of the outer tube, is not projected outside the inner surface of the spool piece. Therefore, the installation places of the O-rings which are a seal member are reduced and the time required for maintenance of the control rod drive mechanism can be shortened.

Abstract: A magnetic jack control rod drive rod drive system having the magnetic coils that operate the moving parts of the drive system wound from anodized aluminum magnet wire or ceramic coated nickel clad copper and enclosed within a hermetically sealed housing that is pressurized with helium.

Abstract: An improved actuator assembly including an eccentric leadscrew actuator assembly with a housing having a stator and a plurality of coils is provided. A rotor is arranged radially inwardly from the stator and includes a first threading on a radially inner surface. A shaft is arranged in a fixed axial position and radially inwardly from the rotor, and includes a second threading on a radially outer surface that engages the first threading of the rotor. A bearing assembly is fixed to the rotor, and the bearing assembly supports an eccentric ring connected to the rotor. The rotor rotates eccentrically around the shaft based on energization of the plurality of coils of the stator. The rotor is axially displaceable by rotation thereof via rolling engagement of the first threading of the rotor and the second threading of the shaft along an axially extending tangent line.

Abstract: A cam is immersed in water at an elevated temperature and/or pressure. A reciprocating cam follower also immersed in the water contacts a surface of the cam. The cam follower includes a permanent magnet. An electrically conductive coil is magnetically coupled with the permanent magnet such that movement of the cam follower induces an electrical signal in the electrically conductive coil. A sealed housing also immersed in the water contains the electrically conductive coil and seals it from contact with the water. Leads of the coil are electrically accessible from outside the sealed housing and from outside the water. Alternatively, the cam includes magnetic inserts, the cam follower is replaced by a sensor arm of magnetic material, and the sensor arm and/or the inserts are magnetized whereby rotation of the rotary element causes time modulation of the magnetic coupling and induces coil voltage.

Abstract: A fine motion control rod drive mechanism handling apparatus attaches a fine motion control rod drive mechanism having a control rod drive mechanism body, a spool piece, a motor bracket and a motor unit to a reactor pressure vessel, and detaches it from the reactor pressure vessel. The fine motion control rod drive mechanism handling apparatus is provided with a bolt wrench assembly, a motor unit attachment mounted to the bolt wrench assembly, for meshing a first gear of a first gear coupling on a spool piece side with a second gear of a second gear coupling on a motor unit side, and a rotation mechanism mounted to the bolt wrench assembly, for rotating the motor unit attachment.

Abstract: A control rod drive mechanism (CRDM) for use in a nuclear reactor, the CRDM comprising: a connecting rod connected with at least one control rod; a lead screw; a drive mechanism configured to linearly translate the lead screw; an electromagnet coil assembly; and a latching assembly that latches the connecting rod to the lead screw responsive to energizing the electromagnet coil assembly and unlatches the connecting rod from the lead screw responsive to deenergizing the electromagnet coil assembly. The latching assembly is secured with and linearly translates with the lead screw, while the electromagnet coil assembly does not move with the lead screw. The electromagnet coil assembly is at least coextensive with a linear translation stroke over which the drive mechanism is configured to linearly translate the lead screw.

Abstract: Disclosed embodiments include electromagnetic flow regulators for regulating flow of an electrically conductive fluid, systems for regulating flow of an electrically conductive fluid, methods of regulating flow of an electrically conductive fluid, nuclear fission reactors, systems for regulating flow of an electrically conductive reactor coolant, and methods of regulating flow of an electrically conductive reactor coolant in a nuclear fission reactor.

Abstract: A digital rod control system that employs separate power modules to energize the respective coils of a magnetic jack control rod drive rod drive system so that two, independently powered grippers can simultaneously support the control rod drive rod when it is not in motion to avoid dropped rods. The basic building block of the system is two or more selecting cabinets which receive multiplex power from at least one moving cabinet and are under the control of a single logic cabinet. Each of the cabinets include monitoring features to confirm the reliability of the system.

Abstract: Control rod drive mechanisms (CRDMs) include CRDM motors, and a support assembly provides bottom support of the CRDMs and includes a lateral alignment plate with openings receiving upper portions of the CRDMs. The upper portions of the CRDMs include compliance features engaging the openings of the lateral alignment plate. The compliance features may comprise angled leaf springs that wedge into the openings of the lateral alignment plate. In some embodiments the upper portion of each CRDM includes straps securing one or more cables to the upper portion of the CRDM, and the angled leaf springs are cut into or welded onto ends of the straps. Some embodiments further include a pressure vessel and a nuclear reactor core comprising fissile material disposed the pressure vessel, and the CRDM is an internal CRDM disposed in the pressure vessel along with the support assembly.

Abstract: A nuclear reactor includes a nuclear reactor core comprising fissile material and a pressure vessel containing the nuclear reactor immersed in primary coolant water at an operating pressure. The pressure vessel has a vessel penetration passing through a wall of the pressure vessel. An electrical feedthrough seals the vessel penetration and has an outside electrical connector mounted at the pressure vessel. The outside electrical connector is at atmospheric pressure. The electrical feedthrough may include a flange disposed inside the pressure vessel and sealing against an inside surface of the wall of the pressure vessel. The outside electrical connector of the electrical feedthrough may be inset into the wall of the pressure vessel.

Abstract: An internal control rod drive mechanism (CRDM) including an electric motor is disposed in a nuclear reactor and further includes a support surface with sealed electrical connectors electrically connected with the electric motor power the motor. The internal CRDM is disposed on a support element secured inside the nuclear reactor. The support element includes sealed electrical connectors mating with the sealed electrical connectors on the support surface of the internal CRDM to power the electric motor. The sealed electrical connectors may be sealed glass, ceramic, or glass-ceramic connectors welded onto the ends of the MI cables extending from the motor. Springs, are disposed between the mating sealed electrical connectors of the support element and the support surface. A purge line is integrated with each mated connection.

Abstract: An integral pressurized water reactor (PWR) comprises: a cylindrical pressure vessel including an upper vessel section and a lower vessel section joined by a mid-flange; a cylindrical central riser disposed concentrically inside the cylindrical pressure vessel and including an upper riser section disposed in the upper vessel section and a lower riser section disposed in the lower vessel section; steam generators disposed inside the cylindrical pressure vessel in the upper vessel section; a reactor core comprising fissile material disposed inside the cylindrical pressure vessel in the lower vessel section; and control rod drive mechanism (CRDM) units disposed inside the cylindrical pressure vessel above the reactor core and in the lower vessel section. There is no vertical overlap between the steam generators and the CRDM units.

Abstract: A power distribution plate (PDP) sits on top of a support plate. Control rod drive mechanism (CRDM) units are mounted on top of the PDP, but the PDP is incapable of supporting the weight of the CRDM units and instead transfers the load to a support plate. The PDP has receptacles which receive cable modules each including mineral insulated (MI) cables, the MI cables being connected with the CRDM units. The PDP may further include a set of hydraulic lines underlying the cable modules and connected with the CRDM units. The cable modules in their receptacles define conduits or raceways for their MI cables and for any underlying hydraulic lines.

Abstract: A standoff supporting a control rod drive mechanism (CRDM) in a nuclear reactor is connected to a distribution plate which provides electrical power and hydraulics. The standoff has connectors that require no action to effectuate the electrical connection to the distribution plate other than placement of the standoff onto the distribution plate. This facilitates replacement of the CRDM. In addition to the connectors, the standoff has alignment features to ensure the CRDM is connected in the correct orientation. After placement, the standoff may be secured to the distribution plate by bolts or other fasteners. The distribution plate may be a single plate that contains the electrical and hydraulic lines and also is strong enough to provide support to the CRDMs or may comprise a stack of two or more plates.

Abstract: An electromagnet comprises a plurality of nested freestanding electrically insulating former layers, and electrically conductive wire wrapped around the outsides of the freestanding electrically insulating former layers to define a multilayer electrical coil in which adjacent layers of the multilayer electrical coil are spaced apart by intervening freestanding electrically insulating former layers. Electrically energizing the multilayer electrical coil generates a magnetic field inside the multilayer electrical coil. In some embodiments the electrically conductive wire is bare wire not having electrical insulation. In some embodiments the former layers comprise a ceramic material. In some such embodiments the electromagnet further comprises a ferromagnetic core disposed inside the multilayer electrical coil. An electric motor employing such an electromagnet as a stator pole is also disclosed.

Abstract: A magnetic jack control rod drive mechanism for a nuclear reactor in which the stationary gripper coil, moveable gripper coil and lift coil are constructed with ceramic or quartz insulation.

Abstract: A magnetic jack control rod drive rod drive system having the magnetic coils that operate the moving parts of the drive system wound from anodized aluminum magnet wire or ceramic coated nickel clad copper and enclosed within a hermetically sealed housing that is pressurized with helium.

Abstract: A digital rod control system that employs separate power modules to energize the respective coils of a magnetic jack control rod drive rod drive system so that two, independently powered grippers can simultaneously support the control rod drive rod when it is not in motion to avoid dropped rods. The basic building block of the system is two or more selecting cabinets which receive multiplex power from at least one moving cabinet and are under the control of a single logic cabinet. Each of the cabinets include monitoring features to confirm the reliability of the system.

Abstract: A control rod drive mechanism (CRDM) for use in a nuclear reactor, the CRDM comprising: a connecting rod connected with at least one control rod; a lead screw; a drive mechanism configured to linearly translate the lead screw; an electromagnet coil assembly; and a latching assembly that latches the connecting rod to the lead screw responsive to energizing the electromagnet coil assembly and unlatches the connecting rod from the lead screw responsive to deenergizing the electromagnet coil assembly. The latching assembly is secured with and linearly translates with the lead screw, while the electromagnet coil assembly does not move with the lead screw. The electromagnet coil assembly is at least coextensive with a linear translation stroke over which the drive mechanism is configured to linearly translate the lead screw.

Abstract: A method for recognizing the step movement sequence of a control rod drive mechanism of a nuclear reactor, which withdraws and inserts a control rod of a nuclear reactor, includes the steps of: measuring current and voltage flowing through an electromagnetic coil used in the control rod drive mechanism of the nuclear reactor; calculating inductance of the coil by using the measured current and voltage; calculating a distance between a rotor and a stator of the control rod drive mechanism on the basis of the calculated inductance; and recognizing the step movement sequence of the control rod drive mechanism on the basis of the calculated distance. This method ensures good reliability in determining the step movement sequence, allows easy implementation using a digital signal processor, and is hardly affected by external factors such as noise.

Abstract: A system and method for monitoring rod moving coils in nuclear power system. The system ensures that these coils are each functioning properly, and thus prevent movement of the other coils when a dysfunctional coil is detected. The method for accomplishing this monitoring is to provide constant power to all of the coils and to measure the negatively induced EMF from this induction. This level of EMF is then compared to a standard EMF. When the EMF level is below a threshold limit, which may be either preset or calculated from a variety of other variables, a signal is sent to an alarm.

Abstract: A method for measuring the drop time of a rod in nuclear reactor with the rod position indication system coils remaining energized. The signal generated at the coils includes both the rod drop trace and the coil power. A filter is applied to separate the rod drop trace from the coil power. The drop time of all rods in a reactor can be measured simultaneously in a single test. Furthermore, the test data results are plotted automatically with plot overlay capability to compare rod drop traces to the results of previous tests or to compare an individual rod to another within the same test.

Abstract: A position verification apparatus comprising a movable member disposed within and movable with respect to a housing containing the movable member, a means for generating a magnetic field within the housing, a first magnetically responsive means for sensing the position of the movable member and outputting a signal indicative of the position of the movable member, a second magnetically responsive means for sensing the presence of the movable member and outputting a signal indicative of the position of the movable member and a means for comparing the signal output from the first magnetically responsive means and the signal output from the second magnetically responsive means.

Abstract: To reduce the manufacturing processes of a control rod and shorten the time required for manufacturing a control rod, for the lower part support member 7, the thin parts 11A and 11B are formed in the neighborhood of each of the left and right sides of the window 8. In the left and right sides of the pull-up handle 9, the grooves 17A and 17B are formed respectively. The groove 17B is deeper than the groove 17A. The thin part 11A is fitted into the groove 17A and the thin part 11B is fitted into the groove 17B. The gap formed between the end of the thin part 11B and the bottom of the groove 17B is larger than the gap formed between the end of the thin part 11A and the bottom of the groove 17A. Therefore, the thin part 11A can be simply fitted into the groove 17A.

Abstract: The electromagnetic drive mechanism for the control rods of a nuclear reactor has a stationary gripper and coil, a movable gripper and coil, and a lifting armature and coil for moving the movable gripper to advance or retract the control rods in steps. A coil current driver responsive to a controller provides currents to the coils individually and in combinations. During the operations, coil current signals are sensed, sampled, digitized and processed to generate coil current data such as amplitude as a function of time. The measured coil current data is compared to nominal current data as well as historical current data, and the historical data is updated or appended to include the measured data. The comparison includes a check for correct timing relationships, such as the timing of the current notch occurring due to increased inductance upon pull-in of a gripper.

Abstract: A control rod mechanism for transmitting the rotation of an electric motor via a drive shaft to an elevator apparatus for raising and lowering a hollow piston on an upper end thereof, which is provided a control rod that controls the output of a nuclear reactor. The control rod mechanism is used to insert the control rod into a reactor core or remove it therefrom, and also to rapidly insert the control rod into the reactor core by the injection of hot water to force the hollow piston upward. The control rod mechanism includes a magnetic coupling having an inner magnet, which is divided into a plurality of parts and is disposed at a lower portion of the drive shaft in order to transmit the rotational power of the electric motor to the drive shaft. The control rod mechanism also includes a drive-side outer magnet, which is divided into a plurality of parts and is provided on a rotary shaft of the electric motor in an arrangement on an outer side of the inner magnet.

Abstract: In a drive device of control rod drive mechanisms, a large number of control rod drive mechanisms are divided into a plurality of groups, and there are provided, for each group, a control rod changeover device, and an inverter power source and inverter controller constituting the drive power source. The drive device comprises a control unit that receives control rod position signals from each of the control rod drive mechanisms and that outputs control signals to the control rod changeover device and inverter controller, and a man-machine device constituting an interface with the operator, that outputs control rod drive information to this control unit.

Abstract: A control rod drive having a magnetic coupling device which eliminates the need for packing-type seal assemblies for preventing leakage from the reactor pressure vessel adjacent the spindle. The magnetic coupling device includes a driving rotor and a driven rotor separated by a pressure barrier which forms part of the reactor pressure boundary. The driven rotor and the driving rotor are coupled magnetically so that the driven rotor rotates in response to rotation of said driving rotor, whereby the control rod displaces in response to operation of the drive motor. The driven and driving rotors are each constructed by stacking a plurality of circular magnetic rings concentric with a centerline axis. Each circular ring has multiple poles circumferentially distributed thereon. An anti-rotation device is incorporated to prevent free rotation of the spindle when the drive motor is removed during maintenance operations. The anti-rotation device includes a push rod actuator which penetrates the pressure barrier.

Abstract: A boiling water reactor includes a pressure vessel containing a reactor core, chimney, steam separator assembly, and steam dryer assembly therein, with the vessel being filled with reactor water to a normal water level through the steam separator assembly. A plurality of control rod drives extend downwardly from the bottom of the pressure vessel and are operatively joined to control rods extending downwardly into the reactor core. The chimney includes a plurality of channels disposed above the core and laterally spaced apart to define guide slots for receiving the control rods as they are selectively translated upwardly out of the core by the control rod drives. The chimney has a vertical height for increasing the normal water level above the reactor core and for providing a space for the control rods withdrawn from the reactor core by the bottom-mounted control rod drives.

Abstract: Apparatus for sensing and transmitting a signal indicative of the position of a movable ferromagnetic member relative to a fixed structure within which the member moves. The apparatus includes a plurality of magnetic circuit arrangements arranged uniformly along the outside of the fixed structure. Each magnetic circuit arrangement includes a pair of magnets and a pair of arcuate-shaped magnetic path elements extending circumferentially about the fixed structure. A plurality of magnetic field responsive position transmitters are positioned adjacent the magnetic circuit arrangements for sensing the presence of the movable ferromagnetic member at predetermined positions within the fixed structure. The apparatus is particularly useful for monitoring the position of control rods in a nuclear reactor because the monitoring is done from outside the sealed structure.

Abstract: A segmented electromagnetic coil assembly for use in a magnetic jack type of drive mechanism used to move control rods within a nuclear reactor. The coil assembly has a plurality of individual magnetic coils spaced around and against the non-magnetic housing which contains the control rod drive shaft.

Abstract: A fast-acting nuclear reactor control device for moving and positioning a fety control rod to desired positions within the core of the reactor between a run position in which the safety control rod is outside the reactor core, and a shutdown position in which the rod is fully inserted in the reactor core. The device employs a hydraulic pump/motor, an electric gear motor, and solenoid valve to drive the safety control rod into the reactor core through the entire stroke of the safety control rod. An overrunning clutch allows the safety control rod to freely travel toward a safe position in the event of a partial drive system failure.

Abstract: A drive for moving a control rod in a pressure vessel containing a pressurized fluid includes a spindle disposed solely within the pressure vessel, which spindle is effective for moving the control rod upon rotation thereof. A driven rotor is fixedly joined to the spindle within the pressure vessel for rotating the spindle, and the driven rotor is selectively rotated in first and second opposite directions without the need for packing-type seal assemblies for preventing leakage of the pressurized fluid from the pressure vessel adjacent to the spindle.

Abstract: Control clusters, each of which comprises a plurality of neutron-absorbing rods, are operable by means of electromagnetic mechanisms whose coils are powered by power bridges driven from a control desk (11). The control system includes a controlling hard-wired logic circuit (12) serving the desk and supervising a plurality of hard-wired logic interfaces each of which serves a subgroup (10) of electromagnetic mechanisms for a determined number of clusters. The static power assemblies (9) each including a hard-wired logic interface and the power bridges of the subgroup(s) (10) served thereby are successively and independently replaced by at least one electronic power assembly (23) constituted by a computer and the power bridges of a subgroup served thereby.

Abstract: A linearly operating motor for stepwise advance of a driven member (11), such as a shaft, comprises an elongated body (10) with length variable properties, and means (15) for changing the length of said body (10). The driven member (11) is provided with at least one locking member (12), whereby at length increase of said body (10) the locking member (12) is arranged, by means of said length increase, to be brought into engagement with said driven member (11) and said body (10) is adapted to act upon the locking member (12) in such a manner the locking member and the driven member (11) are displaced at length increase of the elongated body (10).

Abstract: A latch and linkage arrangement in a nuclear reactor control rod drive mechanism includes a latch having an elongated body with opposite ends and opposite side edges and multiple latch teeth defined along one of body side edges between the opposite ends. The arrangement also includes a plurality of links. A first link pivotally connects with the latch body adjacent one end and is pivotally connected to an electromagnetic armature for applying a motive force to the latch body through the first link. Second and third links are pivotally connected to the latch body and to a support tube in parallel relationship to one another so as to define a parallelogram therewith such that when the motive force is applied to the body via the first link the latch body and thereby the latch teeth undergo curvilinear movement toward and away from a latching position.

Abstract: A nuclear reactor control bar drive device with mobile valve is provided, comprising a cluster guide placed above the core, a casing containing a drive mechanism connected to the inside of the reactor by a sheath passing sealingly through the lid of a vessel containing the core, a control shaft movable vertically in the sheath, connecting the mechanism to the bar and passing, with radial clearance, through an upper plate for closing the guide, as well as a thermal protection sleeve interposed radially between the shaft and the sheath and able to bear by an end piece on said upper plate. The sleeve is pierced, below the sheath, with a calibrated passage for intake of fluid into the guide through the clearance and a non return valve is disposed between the sleeve and the sheath, is movable vertically with respect thereto and co-operates with a seat of the sheath for allowing the fluid to flow only towards the drive mechanism.

Abstract: A pressurized water nuclear reactor comprises a normally vertical main vessel externally duplicated by a confinement enclosure. The main vessel contains a simplified primary circuit essentially incorporationg the reactor core and an annular steam generator arranged in such a way that the circulation of water, pressurized once and for all during the sealing of the vessel, takes place by natural convection. All the auxiliary circuits, conventionally ensuring cooling on shut down of such a reactor are eliminated, said cooling being ensured by a special arrangement of the space formed between the vessel and the enclosure and by the fact that the latter is immersed in an external cooling liquid, no matter what the slope of the reactor. The shut down of fission reaction in the core is ensured by systems of absorbing elements and by the automatic displacement of part of the reflector in the case of a slope of the reactor.

Abstract: A rod drive control system for nuclear such as boiling water reactors is comprised of a plurality of stepping motors for inserting and withdrawing control rods disposed within the nuclear reactor, which the stepping motors are each provided for each control rod, terminal units which are each provided for each stepping motor and are each provided with a motor controller to drive the related stepping motor and to check the operation of the motor, a central processing unit for transferring an operation signal to the motor control unit and for detecting faults in the terminal units, and transmission lines between the terminal units and the central processing unit.

Abstract: Mechanism for displacing and securing the rod of a nuclear reactor control bar, comprising an enclosure coaxial with the rod and forming a hydraulic cylinder in which the rod slides while defining a decompression chamber, a device for mechanically securing the rod in its high position, and a positive displacement reciprocating pump inserted between the decompression chamber and the inside of the tank, whose piston is actuated electromagnetically means and causes at each backward and forward movement lifting of given amplitude of the rod and the device for securing the rod in the high position disengagable also electromagnetically.

Abstract: A control device for a PWR includes a plurality of clusters arranged for insertion into and removal from the core and each having a plurality of rods connected to a common carrier vertically slidable in a stationary guide structure and connectable to a drive shaft. First clusters contain neutron absorbing material and are each individually associated with electromagnetic actuation means for adjusting the amount of insertion of the associated one of the first clusters. Second clusters contain a different material and are each individually associated with hydraulic actuation means controllable to cause upward and downward movement. A set of one first cluster and one second cluster is associated with some of said fuel assemblies, with the drive shafts of the two clusters in each set being arranged symmetrically with respect to the axis of a single stationary structure located above the associated fuel assembly and arranged for authorizing mutually independent movement of the first and second clusters.

Abstract: The electromagnetic device is suitable for use in actuating a pressurized water reactor control bar. It comprises a shaft and a fluid-tight casing in which are movable longitudinally a first and a second sets of grippers for gripping the shaft, staggered in the longitudinal direction. The first set of grippers is associated with a movable pole co-operating with a holding coil, carried by the casing and movable by energization and de-energization of the coil between a position in which the first set of grippers holds the shaft and a position in which it releases it. The second set of grippers is associated with a movable plunger co-operating with a transfer coil and movable by energization and de-energization of the transfer coil to and from a position in abutment against an other pole. The other pole is movable between two positions spaced apart by a given step.

Abstract: Magnetic actuators with dogs for positioning regulating rods in a nuclear reactor. The dogs (2) for lifting and/or holding the control shaft (1) are provided with at least two teeth (4) separated by a distance equalling that separating two successive grooves (3) of the shaft (1).

Abstract: A safety device to be applied to the vertical displacement of, for example, the control rods of a nuclear reactor, comprises the combination of a stator placed on the outside upper part of an impervious, nonmagnetic cylinder within the inside of which a rotor is mounted about its shaft, free in axial translation, with the shaft rotatable with the rotor but fixed in translation, and with the rotation of the shaft transferred to a hollow threaded rod which will transfer rotation to a nut slidable vertically inside the cylinder, supporting the control rods therebelow; the rotor also controlling the opening and closing of a jaw for holding and releasing the hollow threaded rod.

Abstract: A multi-function magnetic jack control drive mechanism for controlling a nuclear reactor is provided. The mechanism includes an elongate pressure housing in which a plurality of closely spaced drive rods are located. Each drive rod is connected to a rod which is insertable in the reactor core. An electromechanical stationary latch device is provided which is actuatable to hold each drive rod stationary with respect to the pressure housing. An electromechanical movable latch device is also provided for each one of the drive rods. Each movable latch device is provided with a base and is actuatable to hold a respective drive rod stationary with respect to the base. An electromechanical lift device is further provided for each base which is actuatable for moving a respective base longitudinally along the pressure housing. In this manner, one or more drive rods can be moved in the pressure housing by sequentially and repetitively operating the electromechanical devices.