Abstract: A device for moving a cluster of nuclear reactor control elements, more especially usable for changing the moderation rate of a nuclear reactor, comprising a vertical shaft having nippers cooperating with grabs integral with sub-clusters. Each grab comprises resilient fingers engageable with the nippers and lockable by snap fitting on the fixed upper structure. Each nipper is formed so as to engage resilient fingers and unlock them from the upper structure when the nipper is raised above the position which causes locking of the grab on the structure. A fixed lower structure is provided for causing forced disengagement of the nipper when this latter is lowered beyond the rest position of the grab on this structure. Raising of the nipper then drives the grab by simple bearing force.

Abstract: A control rod driveline and grapple is disclosed for placement between a control rod drive and a nuclear reactor control rod containing poison for parasitic neutron absorption required for reactor shutdown. The control rod is provided with an enlarged cylindrical handle which terminates in an upwardly extending rod to provide a grapple point for the driveline. The grapple mechanism includes a tension rod which receives the upwardly extending handle and is provided with a lower annular flange. A plurality of preferably six grapple segments surround and grip the control rod handle. Each grapple rod segment grips the flange on the tension rod at an interior upper annular indentation, bears against the enlarged cylindrical handle at an intermediate annulus and captures the upwardly flaring frustum shaped handle at a lower and complementary female segment. The tension rods and grapple segments are surrounded by and encased within a cylinder.

Abstract: In a nuclear reactor including a core, a plurality of control rods, a support supporting the control rods and movable for displacing the control rods in their longitudinal direction between a first end position in which the control rods are fully inserted into the core and a second end position in which the control rods are retracted from the core, and guide elements contacting discrete regions of the outer surface of each control rod at least when the control rods are in the vicinity of the second end position, the control rods being longitudinally movable relative to the guide elements to thereby cause the outer surface of the control rods to experience wear as a result of sliding contact with the guide elements, there is provided a displacement device operatively coupled to the control rods for periodically rotating the control rods in order to change the locations on the outer surfaces of the control rods at which the control rods are contacted by the guide elements.

Abstract: A method and apparatus for removably attaching a top nozzle to a nuclear fuel assembly to permit easy access to the fuel rods. The quick disconnect top nozzle structure includes guide thimbles which are clearance fitted into an adapter plate of the top nozzle. Load collars are attached to the guide thimbles to support compressive loads such as those imposed by holddown springs. Tensive forces, such as lift forces, are transferred through the top nozzle into peripheral straps of a top spacer grid. The peripheral straps include extensions which resiliently latch onto the top nozzle for ease of assembly and disassembly.

Abstract: A self-actuated shutdown system incorporated into a reactivity control assembly in a nuclear reactor includes pumping means for creating an auxiliary downward flow of a portion of the heated coolant exiting from the fuel assemblies disposed adjacent to the control assembly. The shutdown system includes a hollow tubular member which extends through the outlet of the control assembly top nozzle so as to define an outer annular flow channel through the top nozzle outlet separate from an inner flow channel for primary coolant flow through the control assembly. Also, a latching mechanism is disposed in an inner duct of the control assembly and is operable for holding absorber bundles in a raised position in the control assembly and for releasing them to drop them into the core of the reactor for shutdown purposes.

Abstract: Device for operating a cluster of neutron absorber elements in a pressurized water nuclear reactor, comprising two coaxial control shafts (2, 3), the central shaft (3) being rigidly joined to the cluster of absorber elements. A widened part (22) of this shaft (3) forms a piston (22) which is fitted with segments (35). A pressure difference on either side of a segment (35) permits the clusters of absorber elements to be lifted by acting on the piston (22). The segment (35) is radially expandable and the leaktight sealing of the segment is initiated by entry of the piston (22) into the reduced diameter zone (10) of the shaft (2). The invention applies, in particular, to nuclear reactors with spectral shift employing clusters of fertile elements.

Abstract: A coupling device is disclosed which is in rotation between a motor member and a receiver member. The device has a ratchet ring, a pawl holder ring and a drive ring. The pawl holder ring has stops and pawls with a shoulder and a stop surface and pivots between an engaged position and a disengaged position. The drive ring has drivers engaged in the stops. A contoured cam on the drive ring bears on the pawl shoulder in order to pivot it towards its engaged position. Elastic biasing means are positioned between the driver and one of the stops. The coupling device is adapted for use in the control of control rods in a nuclear reactor.

Abstract: The mechanism has at least one carrier sprocket wheel (18-19) fixed on a horizontal shaft (15) mounted on the body of a grab (4) with pivoting fingers. An apparatus (14) for actuating the pivoting fingers connected to the shaft allows them to open and close to take up or, alternatively, release the absorbent unit. Drive chain wheels (25-26) allow the portions (20-21) of a chain supporting the carrier pulley (18-19) to be moved, either in synchronism to move the absorbent assembly or with a differential movement to actuate the pivoting fingers of the grab (4). A single differential pinion apparatus (31-32) allows the two kinds of movement to be carried out.The invention can be applied particularly to the control and emergency shutdown of pressurized water nuclear reactors.

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 magnetic reed switch assembly for activating an electromagnetic grapple utilized to hold a control rod in position above a reactor core. In normal operation the magnetic field of a permanent magnet is short-circuited by a magnetic shunt, diverting the magnetic field away from the reed switch. The magnetic shunt is made of a material having a Curie-point at the desired release temperature. Above that temperature the material loses its ferromagnetic properties, and the magnetic path is diverted to the reed switch which closes and short-circuits the control circuit for the control rod electromagnetic grapple which allows the control rod to drop into the reactor core for controlling the reactivity of the core.

Abstract: The hydraulic drive mechanism comprises an hydraulically actuated rod drive mechanism that cooperates with a pivotable latching mechanism. The pressurized reactor coolant is utilized to raise the drive rod into contact with and to pivot the latching mechanism so as to allow the drive rod to pass the latching mechanism. The pressure in the housing is then equalized which allows the drive rod to move downwardly into contact with the latching mechanism but remain in a raised position with respect to the reactor core. Once again, the reactor coolant pressure may be utilized to raise the drive rod and thus pivot the latching mechanism so that the drive rod passes above the latching mechanism. Again, the mechanism pressure can be equalized which allows the drive rod to fall and pass by the latching mechanism so that the drive rod approaches the reactor core.

Abstract: The invention relates to an actuating device for two clusters of control rods movable vertically in one and the same fuel array of the core of a nuclear reactor.The first cluster, used for running the reactor, is connected to a first actuating rod (2), the movements of which are effected by a mechanism (27, 28, 29, 30, 34). This rod (2) carries hooking fingers (41), the operation of which is effected by a device (45) mounted slidingly on the end of the rod (2). The device (45) causes the closing of the fingers by means of a spring (46), or on the contrary their opening by overstroke movement towards the top of the rod (2). The second cluster remaining fully inserted into the assembly during a part of the operating cycle of the reactor is connected to a second actuating rod (3).

Abstract: In a coupling system for a nuclear reactor control rod and control rod drive, said coupling system being selectively uncouplable by an uncoupling rod, a system of passages for exercising a countervailing force on the uncoupling rod to prevent inadvertent uncoupling during scram.

Abstract: A fine-motion control rod drive for a nuclear reactor, which can be disassembled in sections. The drive includes a spindle defining a sealing surface to prevent spillage after the drive motor is removed. A spline connection with a sliding key arrangement permits the shaft of the drive motor to be separated from the spindle during disassembly. The drive motor is effective for uncoupling the control rod drive piston from the control rod prior to disassembly.

Abstract: Reactivity control assembly for nuclear reactor comprises supports stacked above reactor core for holding control rods. Couplers associated with the supports and a vertically movable drive shaft have lugs at their lower ends for engagement with the supports.

Abstract: Coupler for absorber rods being suspended during operation of nuclear reactors including a plurality of actuating elements being movable for individually and jointly releasing the coupler, the movement of each of the actuating elements for releasing the coupler being independently controllable.

Abstract: A device for providing translatory movement of the control rods inside the closed vessel of a nuclear reactor. The rotor of the drive motor for a screw/nut assembly has fixed to it two pivoting arms formed in the poles of the rotor, and these serve as latching members which keep the screw in its raised position. A tubular casing locks these arms in the opened position while the screw is being raised after the control rod has been allowed to fall into the core of the reactor.

Abstract: The latching mechanism comprises a pivotable member that cooperates with a contact member for coupling the contact member to the pivotable member. A drive mechanism moves the contact member into contact with the pivotable member thereby pivoting the pivotable member and allowing the contact member to seat in the pivotable member. A biasing mechanism urges the pivotable member into its initial position. The drive mechanism can be also utilized to release the contact member from the pivotable member.

Abstract: Apparatus for controlling a nuclear reactor by vertical displacement of a unit absorbing neutrons, comprising, inside a sealed enclosure (1) in communication with the interior of the reactor, a movable magnetic piece (6) connected to a control shaft (3) which is itself connected to the absorbent unit. This magnetic piece (6) has at least two radial projections (7). The magnetic piece (6) is displaced by an inductor (10) with at least two pole shoes (16) corresponding to the projections (7) on the magnetic piece (6) and allowing magnetic coupling between the inductor (10) and the magnetic piece (6). The inductor (10) and its displacement device (30, 32, 33) are disposed outside the sealed enclosure (1). A control means (38) allows the control shaft (3) to be uncoupled from a member (36, 37) assuring its suspension so as to drop the absorbent unit in the event of emergency shutdown. The apparatus is particularly applicable to control rods of pressurized water nuclear reactors.

Abstract: Nuclear reactor core safety rod release apparatus comprises a control rod having a detent notch in the form of an annular peripheral recess at its upper end, a control rod support tube for raising and lowering the control rod under normal conditions, latches pivotally mounted on the control support tube with free ends thereof normally disposed in the recess in the control rod, and cam means for pivoting the latches out of the recess in the control rod when a scram condition occurs. One embodiment of the invention comprises an additional magnetically-operated latch for releasing the control rod under two different conditions, one involving seismic shock.

Abstract: Nuclear reactor safety rod release apparatus comprises a ring which carries detents normally positioned in an annular recess in outer side of the rod, the ring being held against the lower end of a drive shaft by magnetic force exerted by a solenoid carried by the drive shaft. When the solenoid is de-energized, the detent-carrying ring drops until the detents contact a cam surface associated with the lower end of the drive shaft, at which point the detents are cammed out of the recess in the safety rod to release the rod from the drive shaft. In preferred embodiments of the invention, an additional latch is provided to release a lower portion of a safety rod under conditions that may interfere with movement of the entire rod.

Abstract: The nuclear reactor shutdown system comprises a temperature sensitive device connected to a magnetic latch of a neutron absorbing mechanism. The temperature sensitive device is disposed in the neutron absorbing mechanism in such a manner that it is exposed to the reactor coolant so that when the reactor coolant temperature rises above a specific level, the temperature sensitive device will cause the magnetic latch to open and allow neutron absorbing material to enter the reactor core. The temperature sensitive device comprises temperature sensitive material which may be a temperature sensitive resistor sometimes referred to as a thermistor. The thermistor is a device wherein its resistivity significantly increases with increase in its temperature such that when its temperature has significantly increased, the current passing through this system substantially decreases.

Abstract: Device for the remote coupling and uncoupling of two elements of great length disposed coaxially and end to end, comprising an internal actuating sleeve (14) mounted for rotation on one of the elements (1, 5) and rigidly connected to a rod (10, 67) comprising, at its end, an actuating member (12), the rotation of which enables the coupling and the uncoupling to be effected by spacing apart or release of resilient members (8, 9) assuring the junction of the two elements (1, 5). A pin (17) is disposed transversely at the end of the assembly consisting of the internal sleeve (14) and the rod (10, 67), opposite to the end carrying the actuating member (12). An external sleeve (28) of larger diameter than the diameter of the internal sleeve (14) remaining in a fixed position, whereas the two elements (1-5) are displaced in the direction of their axis, comprises slots (45, 47) in which the pin (17) can engage.

Abstract: A typical embodiment of the invention provides a nuclear fuel assembly lock structure for control rod guide tubes. Illustratively, a sleeve telescopes over an end portion of a control rod guide tube which bears against an internal shoulder of the tube. The upper end of the sleeve protrudes beyond the control rod guide tube spider and is locked in place by means of a resilient cellular lattice or lock that is seated in a mating groove in the outer surface of the sleeve. A special tool is provided for disengaging the entire lock structure, washer, spider, spring and grill from the end of the fuel assembly in order to enable these components to be removed in an assembled state and subsequently replaced on the fuel assembly after inspection and repair.

Abstract: A technique is provided for engaging and disengaging burnable poison rods from the spider in a fuel assembly. The cap on the end of each of the burnable poison rods is provided with a shank that is received in the respective bore formed in the spider. A frangible flange secures the shank and rod to the spider. Pressing the shank in the direction of the bore axis ruptures the frangible flange to release the rod from the spider.

Abstract: An inherent shutdown system for a nuclear reactor having neutron absorbing rods affixed to an armature which is held in an upper position by a magnetic flux flowing through a Curie temperature material. The Curie temperature material is fixedly positioned about the exterior of an inner duct in an annular region through which reactor coolant flows. Elongated fuel rods extending from within the core upwardly toward the Curie temperature material are preferably disposed within the annular region. Upon abnormal conditions which result in high neutron flux and coolant temperature, the Curie material loses its magnetic permeability, breaking the magnetic flux path and allowing the armature and absorber rods to drop into the core, thus shutting down the fissioning reaction. The armature and absorber rods are retrieved by lowering the housing for the electromagnet forming coils which create a magnetic flux path which includes the inner duct wall. The coil housing then is raised, resetting the armature.