Abstract: A boiling water reactor has a plurality of control rods disposed in the reactor and adapted to be driven independently by corresponding control rod driving mechanisms, each of the control rod driving mechanisms having a hydraulic piston adapted to be actuated by pressurized water supplied thereto through a hydraulic unit annexed to each control rod driving mechanism to drive the associated control rod into and out of the reactor core. The boiling water reactor has a system for controlling the driving water for the control rod driving mechanisms. The control rod driving water control system has a control rod driving water control unit which controls the direction and velocity of movement of the hydraulic pistons. The control rod driving water control unit is used commonly for a plurality of control rod driving mechanisms.

Abstract: The reactor has a pressure vessel receiving a coolant and a reactor core. The core has vertically movable control rods to which absorber rods are secured. Each tubular control rod extends, with the interposition of an annular gap, around an immobile guide rod which is also tubular and which is longer than the control rod. To move the control rods, coolant is supplied from the pressure vessel under pressure to the interior of the guide rods. The annular chamber communicates by way of communicating bores with the interior of the associated guide rod and, by way of at least two annular restrictions providing different restrictors with the pressure vessel interior. One restrictor is disposed at the top end of the associated control rod and the other restrictor at the bottom end thereof.The control rods move axially upwards in response to an increasing quantity of coolant in the guide rod interiors and downwards in response to a decreasing quantity of coolant in the guide rod interiors.

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 mechanical drive system (10) for moving alternate nuclear reactor fuel rods (14) within the nuclear reactor core (12) and relative to the remaining stationary nuclear reactor fuel rods (16) so as to axially displace the movable fuel rods (14), and enriched and natural uranium fuel zones defined therein, relative to similarly defined enriched and natural uranium fuel zones within the stationary fuel rods (16) in order to optimize utilization of excess or free neutrons produced within the nuclear reactor core within a fuel cycle. The nuclear reactor fuel rods (14, 16) all have a length which is less than that of standard-sized nuclear reactor fuel rods, and therefore, a plenum chamber (20) is able to be defined between an upper core plate (22) and an auxiliary upper core plate (24).

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: 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: An apparatus is disclosed which measures forces resisting the movement of pistons in a control rod drive mechanism in a nuclear reactor and which includes pressure sensing means and further includes hydraulic circuitry to divert pressurized fluid from a normal operating conduit to a selected shunt conduit containing a valve having a particular fluid control characteristic, said shunt conduit directing the fluid to a selected piston to move said piston and said pressure sensing means measuring the pressure of the fluid during the motion of said piston to give an indication of the force needed to achieve such motion.

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: The drive for an absorber rod for a nuclear reactor has a drive piston guided in a cylinder combined with the absorber rod forming an absorber unit. In order to compensate the forces exerted by the medium of the pressure vessel on the absorber unit and tending to pressure the absorber rod axially outward, an equalizing surface is arranged in the absorber unit. The equalizing surface is exposed on one side to the medium of the pressure vessel and/or the cooling medium of the absorber rod, so that an equalizing force is acting on the absorber unit. In the event of a failure of the drive medium acting on the drive piston of the absorber unit or during fluctuations and changes of the internal pressure in the pressure vessel, the absorber unit remains in its existing position, i.e. no unintentional withdrawal of the absorber rod from the pressure vessel takes place.

Abstract: Braking of the motion of a fluid-actuated drive is provided by a buffer arrangement which is normally sealed to prevent vaporization of the fluid in a buffer cylinder and which isolates the drive piston rings from braking pressures.

Abstract: A nuclear reactor, control rod holding latch permits rapid insertion of the control rod into a reactor core by a ratchet and pawl mechanism arranged to lock the control rod against withdrawal, this being done through a screw which by rotation permits slow withdrawal of the control rod from the core, while keeping the control rod locked against withdrawal other than through the screw action.