Westinghouse Electric Corporation

Samuel Cerni

John F Wilson

Robert K Gjertsen

Pratap K Doshi

A nuclear reactor includes a plurality of upstanding guide thimbles and a plurality of control rods received in the guide thimbles and supported for movement relative to the thimbles between inserted and withdrawn positions. The control rods each include a tubular cladding member and an end plug attached to a lower end of the member. The improvement relates to the end plug having a stabilizing configuration which reduces lateral vibratory motion and contact between the control rod and its respective guide thimble. The end plug has an asymmetrical shape which places its terminal tip end in a position offset to one side of the central axis of the control rod and its end plug. As a result of interaction of the asymmetrical plug tip with coolant flowing along the control rod, a lateral steady-state force is imparted to the end plug which maintains the control rod end plug pressed against the wall of tis respective guide thimble. Several different asymmetrical configurations can be employed on the end plug.

Control rod end plug with a stabilizing configuration

A nuclear reactor includes a plurality of upstanding guide thimbles and a plurality of control rods received in the guide thimbles and supported for movement relative to the thimbles between inserted and withdrawn positions. The control rods each include a tubular cladding member and an end plug attached to a lower end of the member. The improvement relates to an wear sleeve disposed on the end plug so as to provide a contact interface between the control rod and its respective guide thimble. The sleeve is composed of material similar to that of the guide thimble and attached to the end plug by an interlock connection. The interlock connection includes a circumferential groove formed in the end plug and a circumferential protuberance swaged or mechanically roll formed in the sleeve so as to extend into the end plug groove.

Wear sleeve for a control rod end plug

A top nozzle subassembly having a hold-down device incorporated therewithin is provided for a nuclear reactor fuel assembly. The subassembly is slidably mounted on the upper ends of the control rod guide thimbles and is removably attached by internally threaded collars which threadably mate with external threads provided on the upper ends of the guide thimbles. Unthreading of the collars allows the subassembly to be removed from the fuel assembly to gain top access to the fuel rods within the fuel assembly. The invention also includes a special tool for threading and unthreading of the collars.

Removable top nozzle and tool for a nuclear reactor fuel assembly

An improved water displacer rod includes an elongated hollow thin-walled tube with a pair of end plugs attached to opposite ends of the tube to hermetically seal the tube and a plurality of support pellets disposed in a stacked relationship within the tube. The pellets allow the thin-walled tube to be laterally flexible while still able to resist collapse due to high external pressure. Each pellet is preferably formed of a body having a hollow annular cross-sectional shape and a pair of end webs extends across and closing opposite ends of the body. The body defines a central void and the webs seal the void. Thus, when the pellets are stacked within the tube, each void is sealed individually one from the next. A double barrier is provided in the displacer rod by the hermetically sealed tube and the individually sealed pellets. Even if the tube should fail, moderator water will not flood the tube interior since the stacked pellets occupy and encapsulate substantially all of the empty space within the failed tube. As a result, the displacer rod containing the failed tube will still be able to perform its intended function.

Water displacer rod with hollow annular support pellets having sealed

An improved bottom nozzle of a fuel assembly includes a housing and a modified adapter plate formed by a network of ligaments which extend across the housing and are connected to the side walls of the housing a short distance below its upper peripheral edge so as to define an open region therein. The improved bottom nozzle also includes a debris trap having a structure disposed within the open region of the housing upon the adapter plate and adapted to capture and retain debris carried by collant flowing from openings in the lower core plate of the nuclear reactor to the fuel assembly. The trap structure is composed of a plurality of straps aligned with one another in a crisscross arrangement and defining a plurality of interconnected wall portions which form a multiplicity of small cells each having open opposite ends and a central channel for collant flow through the trap. A plurality of spring-like fingers are punched out of the wall portions and bent to extend into the cell channels toward the downstream end of the trap structure to provide means to capture and retain pieces of debris carried through the channels by flowing coolant. Also, leaf springs are attached to periphery of the structure and engagable with a plurality of recessed shoulders in the housing for releasably locking the trap structure in place in the open region with intersections formed by the straps aligned below the fuel rods of the fuel assembly.

Fuel assembly bottom nozzle with integral debris trap

A secondary source positioning mechanism for a fuel assembly in a nuclear reactor locates an individual one of the secondary sources in a respective guide thimble of the fuel assembly aligned with an opening defined through the upper core plate which overlies the fuel assembly. The positioning mechanism has a tapered locating boss which registers with a chamfer on the lower side of the core plate about one of its openings and a resilient holddown device which resiliently couples the upper end of a rod containing the secondary source to the locating boss in a manner which restrains the upper end of the rod in the lateral direction and positions the secondary source rod in the axial direction.

Individual source positioning mechanism for a nuclear reactor fuel

A non-boron moderator filled rod for a nuclear reactor fuel assembly has a tubular body with a pair of end plugs sealing the opposite ends thereof and defining a chamber within the body. A liquid moderator, such as light water, is contained witin the chamber. One of the end plugs acts as a hydride sink and a hydrogen getter sponge material is disposed adjacent the other end plug.

Light water moderator filled rod for a nuclear reactor

A nuclear reactor fuel rod includes a fuel tube and an improved end plug assembly having a pair of hollow end plugs which seal opposite ends of the fuel tube. Each end plug has an outer body portion with an outside diameter substantially the same as the outside diameter of the fuel tube and an inner body portion of reduced diameter inserted into an end of the tube. Each plug has a cavity defined therein which increases the space within the rod for fission gas expansion. An outer region of the cavity within the outer body portion of the end plug is undercut relative to an inner region of the cavity within the inner body portion of the plug. One of the end plugs also has an insert fitted into its inner body portion which prevents fuel chips from falling into the cavity of the end plug. A slot is formed axially in a side wall of the insert which allows communication of gas from the tube into the cavity of the end plug.

Growing community of inventors

Churchill Boro, PA, United States of America

Samuel Cerni