Westinghouse Electric Corporation

Other

John F Wilson

Robert K Gjertsen

Samuel Cerni

Harry M Ferrari

Pratap K Doshi

John M Shallenberger

Donald G Sherwood

Joseph B Mayers

Hassan J Ahmed

Raymond A George

Robert B Salton

George D Bucher

Robert F Barry

Thomas R Freeman

Ronald P Knott

William E Kirby

David Douglas Seel

Howard F Fensterer

Enrique R Rosal

Walter F Weiland, Jr

James M Pepka

Roosevelt Garrick

William S Thomasma

A fuel pellet surface defect inspection apparatus has an infeed conveyor, a discharge conveyor, and a slide and inspection assembly between the conveyors. The assembly includes a slide defining an inclined track having exit and entry ends adjacent the respective discharge and infeed conveyors. The entry end is at a higher elevation than the exit end. The assembly also includes an inspection station located along the track between its entry and exit ends. The station has lower and upper sound reflectors configured to define an annular inspection chamber through which a pellet moves as the pellet slides down the inclined track. The chamber completely encloses the cylindrical surface of the pellet as the pellet moves through the chamber. An ultrasonic inspection head is mounted at the station and transmits and receives sound energy to and from a pellet as it moves through the chamber such that the sound energy completely surrounds the moving pellet being inspected within the chamber. The inclined track has an upper portion extending to the inspection chamber and a lower portion extending from the inspection chamber and having a shallower slope than the upper portion to cause deceleration of a pellet as it moves from the upper portion to the lower portion. Deceleration reduces the velocity of the inspected pellet as it approaches the exit end of the track and thereby reduces the chance of impacts with the discharge conveyor that might otherwise produce chips and cracks in the pellets.

Pellet slide and inspection assembly in a nuclear fuel pellet surface

A vacuum transfer apparatus for use in en masse vacuum gripping nuclear fuel pellets includes an enclosure defining a vacuum chamber and having an open bottom, a rigid support gridwork spanning and attached to the enclosure open bottom, and a perforated mat attached to the gridwork along a side opposite from the enclosure. The mat is composed of resiliently flexible material and has a matrix of spaced apart holes of a cross-sectional size substantially smaller than the diameter of the pellets. The support gridwork defines a plurality of passages of a cross-sectional size substantially larger than that of the holes in the mat. The gridwork passages provide the sole path for communicating a vacuum from the enclosure chamber to the mat holes for vacuum gripping and holding the pellets at their upper end surfaces against the mat. A perforated tray is employed with the vacuum transfer apparatus for supporting the fuel pellets. The perforated tray has a plurality of openings of substantially the same size and spacing as the holes in the mat. Those of the openings not covered by thy pellets supported on the tray prevent formation of a vacuum between the mat and tray which could prevent lifting of the pellets from the tray.

Random fuel pellet vacuum transfer apparatus

The mechanical spectral shift reactor comprises a reactive core having fuel assemblies accommodating both water displacer elements and control rods for selectively changing the volume of water-moderator in the core. The fuel assemblies are arranged in alternating fashion so that one drive mechanism may move displacer elements in more than one fuel assembly without interfering with the movement of control rods or the corresponding control rod drive mechanisms.

Mechanical spectral shift reactor

A burnable absorber cluster assembly includes a support plate, a plurality of burnable absorber rods, and an improved attachment joint for detachably connecting an upper end of each of the absorber rods to the support plate. The attachment joint includes a plug insert defined on the end of each of the rods, a hollow annular wall extending outwardly from each plug insert, holes defined through the support plate for receiving the plug inserts, and recesses formed in the support plate and connected with the holes therein. Each recess is conical-shaped and extends in flared fashion outwardly from one hole to a maximum diameter greater than the diameter of the hole. The annular wall on each plug insert is deformed into conformity with the shape of one of the recesses for providing an interengaging connection between the insert plug and the support plate in which the plug insert is disposed within the support plate hole. The annular wall is also redeformable upon application of a predetermined axially-directed force on the plug insert so as to remove the plug insert from the support plate hole and thereby detach the rod from the support plate. Also, each recess and annular wall have respective interengaging eccentric portions which prevents the plug insert on each rod end from rotating in its corresponding hole.

Burnable absorber rod push out attachment joint

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 radial neutron reflector for a water moderated nuclear reactor. The space surrounding the nuclear core is provided with a plurality of side-by-side stacked reflector roads having a square cross-sectional shape. Blocks of reflector material having axial grooves are fitted within a square enclosure. The assembly is subjected to high pressures and temperatures which collapse the enclosure onto the blocks eliminating the assembly clearance. The enclosure material flows into the grooves of the blocks leaving wrinkle-free surfaces over the flat remainder of the enclosure. Square shaped reflector rods result in high solid-to-void ratios in the radial reflector region of the reactor. The resulting grooves allow for coolant flow and cooling of the rods.

Radial neutron refelector

A top nozzle adapter plate for use in a fuel assembly of a nuclear reactor includes an upper structural component and a lower functional component supported from the upper component. The fuel assembly has elongated structural members and fuel rods disposed in a predetermined array. The upper structural component of the adapter plate includes spaced and interconnected hubs and ligaments arranged to define substantial open areas for coolant flow therethrough while providing a rigid framework capable of transmitting lifting loads imposed by the fuel assembly. The hubs are connected to the elongated structural members of the fuel assembly. The lower functional component of the adapter plate includes a grid composed of a plurality of spaced and interleaved straps which cross one another to form intersections aligned with individual fuel rods in the array thereof for restraining movement of fuel rods upward from the fuel assembly while defining open channels through the grid for allowing passage of coolant flow therethrough. The grid also contains void areas through which extend the hubs of the upper component. The lower component also includes coolant flow directing means being operable to establish a predetermined desired pressure drop across the top nozzle of the fuel assembly. In one form, the coolant flow directing means is a plurality of tabs connected to the grid straps and extending outwardly therefrom. The tabs are adjustable into various desired positional relationships with respect to the grid channels for controlling coolant flow therethrough. In a modified form, the coolant flow directing means is in the form of a thin flat plate having holes of predetermined desired sizes and shapes formed therein. The plate extends along the interleaved straps of the grid with its holes generally aligned with the open channels of the grid.

Top nozzle adapter plate with fuel rod capture grid having pressure drop

A nuclear reactor fuel assembly bottom nozzle to guide thimble attachment system and method allowing bottom nozzle removal and replacement without inverting the fuel assembly. At manufacture, a bottom-insertable, two-headed bolt secures the bottom nozzle adaptor plate to the guide thimble bottom end plug. The two-headed bolt is unthreadable in the guide thimble from the top of the upright fuel assembly. At reconstitution, a top-insertable bolt fastener secures the replacement or original bottom nozzle adaptor plate to the guide thimble bottom end plug. The bolt fastener is inserted in the guide thimble from the top of the upright fuel assembly. The bolt fastener is unthreadable in the guide thimble from the top of the upright fuel assembly for a second reconstitution. Less preferably, the bolt fastener also can be used for original manufacture (in place of the two-headed bolts previously discussed).

Nuclear fuel assembly bottom nozzle attachment system allowing

A coolant-displacement rod for a nuclear reactor including a stack of zirconium-oxide pellets in cladding of ZIRCALOY-4 alloy. The outer surfaces of certain of the pellets spaced at intervals along the stack are depressed. The cladding grows permanently when exposed to neutron flux but the zirconium oxide is dimensionally stable. Under the hoop stress impressed by the coolant on the cladding, the part of the cladding encircling each of the pellets with the depressed outer surface engages the outer surface compartmentalizing the pellets into sub-stacks. The formation of a long unsupported gap under the cladding which might collapse under the pressure and at the temperature coolant is prevented by forming a plurality of short unsupported gaps instead of one long gap.

Element immersed in coolant of nuclear reactor

An improved arrangement for attaching and reattaching a top nozzle of a reconstitutable fuel assembly includes a sleeve member associated with each guide thimble of the fuel assembly and complementary elements for attaching the sleeve member and the upper end portion of the guide thimble together. The sleeve member includes an inner tubular alignment sleeve portion which receives the guide thimble upper end portion and extends between the upper hold-down and lower adapter plates of the top nozzle. The sleeve member also includes an outer tubular shroud portion having a lower annular flange which underlies a coil spring surrounding the sleeve portion and interconnects the shroud portion and the sleeve portion. The outer shroud portion extends upwardly about a portion of the coil spring for protecting the spring from damage by coolant cross flow from adjacent fuel assemblies. The complementary elements include upper primary and lower secondary interior spaced annular grooves formed on the alignment sleeve portion and a primary exterior bulge formed on the guide thimble upper end portion. The primary bulge extends into the primary annular groove to connect the sleeve portion to the guide thimble. The secondary groove is adapted to receive a secondary exterior bulge, being formed on the guide thimble upper end portion after an initial severance of an upper segment of the upper end portion, for reconnection of the alignment sleeve portion and the severed guide thimble together.

Arrangement and method for attaching and reattaching a top nozzle in a

The hold-down plate of the top nozzle of a fuel assembly is removably attached on the upper extension members of the fuel assembly guide thimbles by an improved structure associated with passageways through the hold-down plate which receive upper end portions of the guide thimble upper extension members. The improved attaching structure includes recesses on the upper end portions of the guide thimble extension members with the recesses terminating at upper terminal edges thereof, elements mounted in the upper hold-down plate and extending therefrom into the passageways of the plate and the recesses of the extension member upper end portions, and a plurality of stop members connectable on the upper end portions of the guide thimble extension members and having overhanging ledges respectively formed thereon which define upper limits of the respective recesses on the extension member upper end portions. The elements are positioned to slide upwardly along the corresponding recesses until making engagement with the ledges on the stop members when the stop members are connected on the corresponding extension member upper end portions for limiting upward movement of the upper hold-down plate along the guide thimble. Also, the elements are positioned to slide upwardly along and past the corresponding recesses when the stop members have been disconnected from the corresponding extension member upper end portions for allowing removal of the upper hold-down plate from the guide thimble.

Reconstitutable fuel assembly having removable upper stops on guide

An integral reusable locking arrangement for a top nozzle of a reconstitutable fuel assembly includes a thin-walled tubular section on the upper end portion of each guide thimble of the fuel assembly above an externally threaded section thereon and an axial section on ecah alignment sleeve of the top nozzle above its lower internally threaded section. The tubular section has an annular circumferential protrusion defined thereon having an external diametric size which is greater than that of the remainder of the tubular section. The axial section on the sleeve has an internal diametric size which is greater than that of the tubular section but less than that of the protrusion. Therefore, rotational movement of the sleeve relative to the guide thimble from its raised toward its lowered position to thread its lower internally threaded section on the externally threaded section of the guide thimble causes interference contact of the axial section with the tubular section protrusion so as to produce a locking force. The locking force which must be overcome in order to unthread the internally threaded section of the sleeve from the externally threaded section of the guide thimble and detach the top nozzle from the guide thimble. The locking force takes the form of a constant torsional drag produced between the tubular section protrusion and the axial section interior surface as the sleeve is rotatably moved relative to the guide thimble between its lowered and raised positions. The circumferential protrusion on the tubular section is axilly displaced from the axial section when the internally threaded section on the sleeve is initially rotatably moved into threaded engagement with the externally threaded section on the guide thimble, whereby the mechanical advantage produced by threading the internally threaded section of the sleeve on the externally threaded section of the guide thimble can be used to overcome the torsional drag and force the sleeve onto the guide thimble.

Integral reusable locking arrangement for a removable top nozzle

The mechanical spectral shift reactor comprises apparatus for inserting and withdrawing water displacer elements from the reactor core for selectively changing the water-moderator volume in the core thereby changing the reactivity of the core. The apparatus may include drive mechanisms for moving the displacer elements relative to the core and guide mechanisms for guiding the displacer rods through the reactor vessel. An array of tubes may be disposed between the guide mechanisms and the fuel assemblies for guidance and minimization of flow induced vibrations of the displacer elements.

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.

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Murrysville, PA, United States of America

John F Wilson