Westinghouse Electric Corporation

Hassan J Ahmed

James L Fogg

John M Beatty

Merle A Parker

John F Wilson

Kenneth S Gerkey

Mark E Wylie

David V Lambert

Mark P Goldenfield

Ralph W Kugler

Nicola G Arlia

Lawrence J Zana

Thomas W Miller

Richard A Pregnall

Michael J Field

John C Lichauer

Steven R Burchill

Roosevelt Garrick

Renny Lacy

Rhonda L Pautler

The girth welds joining the end plugs and the hollow tubes of nuclear fuel rods are inspected automatically using a technique that averages reflectance values, compares the reflectance values to standards defined as proportions of the average, and counts adjacent pixels outside the standards to analyze for defects exceeding a minimum defect size. The minimum defect size is checked by counting the adjacent pixels in mutually perpendicular directions, such as rows and columns in the collected matrix of pixel data. The maximum count in the two directions can be different, for profiling the maximum acceptable defect as to the direction of its extension relative to the tube and/or weld. Tubes are inspected prior to surface treatments that may conceal defects. The tube is fed, illuminated and rotated for at least one revolution at an inspection station, collecting line scans at regular angles synchronously with rotation using a line scan camera coupled to a digitizer to obtain the matrix of data encompassing the girth weld. A numerical processor averages, compares and counts the number of adjacent pixels for assessing weld quality.

Automated girth weld inspection of nuclear fuel rods

A non-contact surface flaw detection system for workpieces such as nuclear fuel pellets transports the pellets continuously along an illuminated path while rotating them. A line scan camera records a series of line scans for the pellets and the resulting values of pellet reflectivity are digitized. Pixel values are compared to thresholds defined adaptively by averaging and/or using a video finite impulse response filter, to generate a binary map of 'good' and 'bad' pixels, that also defines the edges of the pellet in the map. A processor counts and associates bad pixels to logically define and assess blobs of bad pixels. The processor checks for coincidence of the edge pixels with a nominal edge line that best fits the edge, for finding edge flaws. The pellets assessed in this manner are selected or rejected. Camera sensor elements are normalized for gain and offset. Shifting of the pixel data cancels skew produced in scanning moving pellets. Convolution filters cancel isolated bad pixels and enhance contrast at the edge. For processing adjacent areas, the pixel image of the pellets can be tiled, flaws bridging the tile boundaries being assessed as a single blob. The apparatus is preferably arranged for parallel pipeline processing for sidewall and edge defects and can be embodied in a series of modular VME boards.

Non-contact flaw detection for cylindrical nuclear fuel pellets

A method and apparatus for monitoring the laser marking of a bar code label which has been laser marked onto the end of a nuclear fuel tube for unacceptable depth penetration of the heat affected zone. The average gray level value of the bar code label positioned on the end of the nuclear fuel tube is compared with a predetermined standard. In the method disclosed, a bar code label positioned on the surface of the nuclear fuel tube is optically sensed and a set of discrete digital values representative of the depth penetration of the heat affected zone is generated. The average digital value representative of the bar code label is calculated and the average digital value compared to a predetermined standard.

Method and apparatus for monitoring the laser marking of a bar code label

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 method and apparatus for inspecting cylindrically configured pellets for surface defects is disclosed. At least one axially extending linear portion of the peripheral surface of the pellet is optically sensed. A set of discrete digital values representative of the optically sensed linear portion of the pellet surface is generated and the set of digital values is compared to a predetermined standard. Groups of digital values representative of adjacent locations on the surface of the pellet having values greater or less than the predetermined standard are identified. The area of adjacent digital values having a value above the standard, and the area of adjacent digital values having a value below the standard are calculated and compared to a predetermined area. The pellet is rejected when the calculated area exceeds a predetermined area. During inspection, the pellet is moved axially through an inspection station by first and second horizontally positioned substantially parallel and longitudinally extending pellet support rolls. The rolls are spaced a distance from each other less than the diameter of a pellet to be transferred. The rolls are rotated upward and outward from each other and chain dogs are positioned between the spaced rolls for engaging a pellet and moving the pellet along between the spaced pellet support rolls.

Pellet inspection system

A method and apparatus for determining the enrichment of uranium dioxide powder is disclosed. A uranium dioxide powder is contained within a closed receptacle having a top, side and bottom wall surfaces. The receptacle is turned upside down so that the uranium dioxide powder is shifted within the receptacle to obtain a more uniform bulk density of the powder contained therein. The natural gamma radiation emission count of the powder is detected while the receptacle is upside down to determine the enrichment thereof.

Method and apparatus for determining enrichment of uranium dioxide powder

An inspection apparatus and method for testing nuclear fuel rods for helium leaks includes the basic operative steps of constantly leaking helium at a predetermined known value into a test chamber containing a fuel rod to be tested, and sampling the atmosphere within the chamber and measuring the helium in the atmosphere. A measured helium value below a preset minimum helium value indicates a malfunction in the inspection apparatus, whereas a measured helium value above a preset maximum helium value indicates the existence of a helium leak from the fuel rods. On the other hand, a measured helium value between the minimum and maximum helium values indicates the absence of a helium leak from the fuel rod.

Nuclear fuel rod helium leak inspection apparatus and method

A modified inspection apparatus for inspecting nuclear fuel pellets for surface defects includes a pellet guide chute assembly extending through an ultrasonic inspection chamber. The guide chute assembly has a support substrate and a pair of elongated plates attached on respective upper adjacent sides of the substrate. The substrate is composed of a pair of elongated wall sections rigidly attached together to have a V-shaped configuration in cross section. The plates are adjustably attached on the substrate wall sections for supporting a nuclear fuel pellet between and on adjacent longitudinal portions of the plates located in the inspection chamber. The plates have respective slots and cutout regions underlying the pellet at the adjacent longitudinal portions of the plates so as to expose portions of the support substrate wall sections also underlying the pellet such that acoustical energy can be propagated to and from bottom and side portions of the pellet via reflection of the acoustical energy from the exposed wall section portion. Also, an acoustical energy reflecting cover is disposed over the guide chute assembly at the inspection chamber. Further, a pellet position sensing arrangement and a transducer array for transmitting and receiving acoustical energy are included in the modified inspection apparatus.

Nuclear fuel pellet surface defect inspection apparatus

A method and apparatus for passively scanning for the gamma radiation emission count of nuclear fuel contained within a nuclear fuel rod to determine enrichment uniformity are enclosed, and wherein a nuclear fuel rod containing a nuclear fuel is advanced along a linear path of travel and its natural gamma radiation emission count is repeatedly detected at each of a plurality of regularly spaced apart discrete segments along the length of the rod. The outputs from each of the detecting steps are summed to obtain a total gamma radiation count for each segment from which the enrichment values for each segment as well as the average enrichment of said fuel rod may be calculated.

Method and apparatus for passively gamma scanning a nuclear fuel rod

In a nuclear fuel rod identification system, indicia is provided on a nuclear fuel rod in two stages. In the first stage, by use of a laser beam a bar code is applied directly on the fuel rod cladding tube prior to loading it with nuclear fuel and attaching plugs to opposite ends thereof to provide an assembled fuel rod. In the second stage, after loading nuclear fuel into and attaching end plugs to opposite ends of the fuel rod cladding tube with the applied bar code to provide an assembled fuel rod, by use of a laser beam, identification and enrichment symbologies are applied respectively to the side and end of one of the end plugs of the assembled fuel rod.

Method and apparatus for providing fuel rod identification to permit

A fuel assembly grid inspection apparatus includes a precision noncontact measurement device having a source of illumination and a viewing system which define an inspection field of view. The viewing system is adapted to view and record one or more images of an object, such as a fuel assembly grid, located in the field of view to provide information from actual measurements of the grid which can be calculated to determine whether or not it comes within acceptable tolerances of the measurements of a standard grid of the same design. The apparatus also includes a universal fixture adapted to support any one of a variety of grids of different designs within the field of view such that portions of the fixture within the field of view are substantially transparent to the viewing system. The viewing system and the fixture are movable relative to each other in X, Y and Z directions for achieving a complete inspection of all parts of the grid. Typically, the grid being inspected has at least a pair of vertically displaced fuel rod contacting dimples disposed in each of a plurality of cells defined in the grid. The dimples are inspected for perpendicularity with respect to each other by using the viewing system to view them at separate instances but from the same location within the field of view.

Fuel assembly grid inspection apparatus

An apparatus for an integrated and automated fuel assembly inspection system includes a support base, an elongated fixture, top and bottom carriages and a pedestal. The top carriage is mounted to a pair of tracks on the fixture for vertical movement therealong. The pedestal is mounted on the base and aligned with the top carriage for supporting a nuclear fuel assembly therebetween. The bottom carriage has a central opening adapted to receive the fuel assembly therethrough such that the bottom carriage surrounds all sides of the fuel assembly. Also, the bottom carriage is mounted to the tracks for generally vertical movement along the fixture and the fuel assembly. D.C. stepping motors are mounted on the top and bottom carriages and coupled to a gear track for selectively driving the carriages along the fixture. Proximity sensors are movably disposed on the bottom carriage adjacent the sides of the fuel assembly for measuring its envelope when the bottom carriage is moved to and stationed at selected axial positions along the fuel assembly. Lasers and photodetectors are disposed on the top and bottom carriages for continuously monitoring fixture out-of-straightness and performing correction. Capacitive probes are disposed on the bottom carriage for measuring channel spacing between fuel rods of the fuel assembly, and photoswitches and an optical scale are disposed on the bottom carriage and the fixture for measuring fuel assembly length when the bottom carriage has been moved between the bottom and top nozzles of the fuel assembly.

Apparatus for integrated fuel assembly inspection system

Nuclear fuel rods are processed to remove moisture in an oven which is evacuated. Measurement of the moisture content in each of a plurality of nuclear fuel rods (typically 44) is carried out by condensing the vapor derived from one randomly-selected control rod in a nitrogen-liquid cooled trap, collecting the condensed vapor in magnesium perchlorate, and determining the weight of the collected moisture. Moisture from the one fuel rod is condensed, collected and has its weight determined repeatedly in increments until the difference between the weight of a last increment and of a just preceding increment is less than 1 mg. (The permissible content is 6 mg. or less.) The rods have small perforations through which the vapor can escape. The evacuating system includes a main evacuating channel connected directly to the oven and a branch channel connected to the one fuel rod through the cold trap. The temperature of, and the vacuum in, the one fuel rod is the same as for the other rods and the residual moisture content after processing must be the same.

Measurement of moisture content

An interactive system (10) for facilitating assembly of fuel rods into nuclear fuel assemblies having specific grid location requirements for the fuel rods, includes an operator work station (12) adapted for positioning between a supply of fuel rods and a fuel assembly loading magazine (22). Identifying data with each fuel rod is read by the operator with a manual scanner (24) for input and comparison by a computer (28) with the stored data for the particular fuel assembly to be assembled. The proper grid location for the fuel rod is then displayed on a screen (32) prompting the operator to insert the rod through a prompter/detector apparatus (36) mounted on one end of the magazine. In the preferred embodiment, the apparatus (36) includes a pair of motorized, slotted guide bars (54, 56) controlled by the computer (28) to intersect over the proper grid location for the particular fuel rod type. Sensors (92, 94, 95) are provided on the guide bars (54, 56) for automatically detecting insertion and verifying identification of the fuel rod loaded into the magazine through control logic in the computer (28). Alternate embodiments of the prompter/detector apparatus (110, 140 and 170) are disclosed to provide different degrees of prompting to assist the operator to insert each fuel rod in the proper grid location.

Growing community of inventors

Irmo, SC, United States of America

Hassan J Ahmed