Abstract: A method for removing a CRD with the position indicator probe in place. The method allows probe removal to be performed in a low-dose area, thereby effectively reducing the exposure received by the crew removing the probe to nearly zero. An electronic monitoring tool is provided for continuous CRD uncoupled monitoring during drive removal, using the position indicator probe to verify that the drive is uncoupled. The tool is mounted on the CRD removal equipment. The monitoring circuit is connected to selected position switches inside the position indicator probe. These switches are closed when a ring magnet on the drive piston is in proximity to the respective switch. The detected state of the switches can be used to determine whether the index tube/drive piston assembly is being extended as the CRD is lowered out of the housing. Indicator lights are activated to annunciate a coupled condition wherein the index tube is displacing relative to the piston tube as the CRD is lowered.

Abstract: A pellet stack length recording switch, for use in a measurement system having a movable measuring head and a measuring device for measuring a length of a nuclear fuel pellet stack segment, includes a probe for contacting and applying a compression force to an end of the pellet stack segment, a compression spring having a predetermined compression force and cooperating with the measuring head and the probe, a pin mechanism attached to the probe, and a sensor for sensing a position of the pin mechanism and outputting a position signal for triggering a measurement by the measuring device of the length of the pellet stack segment when the compression force applied by the probe is at least equal to the predetermined compression force. The probe may include a slider block, for compressing the spring, and a probe member attached to the slider block. The pin mechanism may include a trip screw for tripping the sensor.

Abstract: A refueling system for a nuclear power plant utilizing a data network to provide for automatic control and enhanced monitoring of the entire fuel transfer process. The refueling system of this invention provides integrated control of the refueling machine within the containment building, the spent fuel handling machine within the fuel storage building, and the fuel transfer system between the buildings. The system provides supervisory control of the overall system operation via a remote control station, while at the same time, having the capability for local on-line control of each element of the system in the event of network failure. The system may automatically identify individual fuel assemblies with an optical scanner. An in-mast sipper connected to the network automatically tests for leaking fuel assemblies. A revised core load pattern and a revised sequence plan can be calculated by the system in the event of the discovery of a leaking fuel assembly.

Abstract: Excore detector measurements are used to generate on-line absolute reactor power in a pressurized water reactor (PWR) by calibrating detector current measurements to the reactor thermal power calculation made at a base time early in reactor cycle while the thermal reactor power measurement is still accurate. Measurements are also made at the base time of the three-dimensional core power distribution and the core inlet temperature. Present core power measurements are then made by measuring the present excore detector current, the most recent three-dimensional core power distribution and the present core inlet temperature. The present core power is then calculated as the ratio of the present detector current to the detector current at the base time multiplied by the reactor thermal power measurement at the base time.

Abstract: An online system for diagnosing operability of a rotating electrical apparatus includes sensors producing electrical variables corresponding to operating conditions of the apparatus, data converters for converting the electrical variables to digital values, a comparator for comparing the values to corresponding predetermined baseline values of the apparatus and producing a corresponding comparison value, and a signalling mechanism for outputting signals related to a period of predicted operability of the apparatus whenever the comparison value exceeds a corresponding predetermined deadband value. The operating conditions may be non-electrical operating conditions, such as a condition of a lubrication system or a bearing of the apparatus. Alternatively, the sensors may sense electrical insulation non-thermal parameters during operation of the apparatus, in order to produce signals related to the operability of an insulator of the apparatus.

Abstract: A reactor core inspection apparatus is disclosed which comprises a hollow tube containing a distally located radial opening, and having an ultrasonic transducer located therein. The tube is connected by a hollow cable to a calibrated degree wheel which allows rotation of the tube once lowered through the top of a partially raised upper internals assembly of a reactor. The transducer is connected to a detector which senses whether one of the fuel assemblies contained within the core has become entangled with the internals assembly prior to full removal of the assembly. If a hangup is detected, the assembly can be lowered in an attempt to disentangle the fuel assembly, to avoid damage.

Abstract: A liquid level instrumentation measurement system for measuring the level of liquid under high pressure in a pressure vessel containing liquid and vapor with non-condensable gases. The system includes a reference leg outside the pressure vessel, a condensing chamber at the upper end of the reference leg defining a vapor space in which vapor condenses to keep the reference leg filled with liquid, a variable leg connected near the bottom of the pressure vessel, and a differential pressure detector connected to both the variable leg and the reference leg for generating a signal proportional to the level of liquid in the pressure vessel. A vent outlet is disposed in the condensing chamber to which a vent leg is connected. The vent leg may be disposed between the vent outlet in the condensing chamber and the variable leg or between the vent outlet and the head vent line which connects the pressure vessel to a main vapor line.

Abstract: A method and a gage for testing uncoupling tools to ensure proper operation prior to use. The uncoupling tool gage simulates the actual conditions under which the uncoupling tool is expected to perform. The gage has a cylindrical guide for slidably receiving a magnet housing. The guide is supported such that it is concentric with respect to the probe of an uncoupling tool to be checked. The magnet housing is placed inside the cylindrical guide and then moved toward the bottom thereof. When the magnet moves into proximity with a switch in the uncoupling tool probe, an indicator lamp in the uncoupling tool illuminates. If the face of the magnet housing is within a range band on the outside of the guide when the indicator is illuminated, then the uncoupling tool is operating properly.

Abstract: A tool for checking the length of a control rod drive measured from the top of the control rod drive flange to the end of the uncoupling rod. The tool is a GO--NO--GO gauge with tight tolerance. The top of the tool supports a gage which has an arm that pivots about an axis parallel to the tool axis. The arm has a stepped notch with a predetermined height equal to the length tolerance range (e.g., 0.0625 inch). The length is considered acceptable when the gage is rotated and the first edge of the stepped notch on the arm just clears the end of the uncoupling rod but the second edge stops the gage from pivoting any further. The length is not acceptable if the first edge of the stepped notch on the arm abuts the uncoupling rod, preventing the gage from pivoting any further, or if the gage misses the uncoupling rod entirely.

Abstract: The device includes a first tubular support (11) carrying on its outside surface means for fixing to a handling tool, a second tubular support (18) mounted coaxially inside the first support (11) for rotation about its axis. A flexible strip (55) carrying a monitoring probe at one of its ends is engaged in a slideway support carried by the second support (18) and including an end part (65) mounted to pivot about an axis which is perpendicular to the axis (25) of the second support (18). The strip (55) is moved translationally along the axial direction (25) by a conveyor bolt (53). The inside surface of the tubular piece (3) is monitored by moving the probe fixed to the end of the flexible strip (55) rotationally about the axis (25) and in axial translation, inside the annular space (8) between the sleeve (5) and the tubular piece (3).

Abstract: A fuel rod position determination apparatus and a method are presented to enable efficient and accurate determination of the positions of the fuel rods in a fuel assembly in which it is not possible to insert a measuring instrument in a straight line through the fuel assembly. The apparatus first measures the positions of the peripheral fuel rods from the outside of the fuel assembly. This operation is continued by inserting sensors into the assembly through the spaces between the fuel rods so as to measure the profiles of the fuel rods. The positions of all the fuel rods including the interior fuel rods are determined on the basis of the profile data, the reference data formed by the peripheral fuel rods, and the known diameter data of the fuel rods.

Abstract: A method for removing a CRD with the position indicator probe in place. The method allows probe removal to be performed in a low-dose area, thereby effectively reducing the exposure received by the crew removing the probe to nearly zero. An electronic monitoring tool is provided for continuous CRD uncoupled monitoring during drive removal, using the position indicator probe to verify that the drive is uncoupled. The tool is mounted on the CRD removal equipment. The monitoring circuit is connected to selected position switches inside the position indicator probe. These switches are closed when a ring magnet on the drive piston is in proximity to the respective switch. The detected state of the switches can be used to determine whether the index tube/drive piston assembly is being extended as the CRD is lowered out of the housing. Indicator lights are activated to annunciate a coupled condition wherein the index tube is displacing relative to the piston tube as the CRD is lowered.

Abstract: A pressurizer vessel of a nuclear power plant contains a liquid and steam both of which function to maintain pressure in a reactor coolant system. A heater support assembly is disposed in an interior portion of the pressurizer vessel and receive a plurality of heaters which are matingly fitted with the heater support assembly for heating the liquid. A temperature detector is operatively connected to the heater support assembly in a structural arrangement which allows for measuring the temperature of the liquid at a plurality of preselected elevations. The temperature detector further includes temperature measuring means for measuring a plurality of temperature readings of the liquid at preselected elevations of the liquid.

Abstract: A combined ultrasonic and eddy-current method and apparatus for non-destructively determining the liner thickness of a zirconium liner provided at the inner surface of a zirconium alloy nuclear fuel rod tube utilizes dimensional data acquired via conventional ultrasonic measurement techniques and impedance data acquired through electromagnetic techniques to calculate liner thickness in accordance with a specific formula. The apparatus utilizes a computer or programmable arithmetic unit with associated memory and I/O devices connected to electromagnetic and ultrasonic measurement subsystems. A particular eddy-current probe arrangement consisting of a differential coil pair is employed to obtain impedance measurements from the outside of the cladding tube. Calibrated reference impedance values for various different inner and outer tube diameters having a constant liner thickness are measured and retained in a memory.

Abstract: A system for simultaneously testing at least two any control rod clusters contained within a reactor vessel, the system comprising a control rod drive mechanism attached to the control rod clusters for retracting the control rod clusters within said reactor vessel to a position suitable for testing. Electrical power means connected to the control rod drive mechanism for supplying electrical power to the control rod drive mechanism and for terminating the power to the control rod drive mechanism and, when terminated, causing said all said control rod clusters to fall into the reactor vessel. A rod position indicator attached to the control rod drive mechanism for monitoring the position of the control rod clusters; and computing means operatively connected to the rod position indicator and receiving a signal representing the fall time of each control rod cluster for generating an elapsed time profile of all the control rod clusters.

Abstract: A method for magnetic coupling compensating a rod position indication system having at least two rod position indicators each having induced noise comprising the steps of applying a sinusoidal current to a primary of the first rod position indicator for inducing a voltage on a first secondary of the first rod position indicator; receiving both the first secondary voltage from the first rod position indicator and a second secondary voltage, induced from the noise, of the second rod position indicator; and deriving a difference of the first and second secondary voltage for obtaining the magnetic coupling compensation.

Abstract: A method and apparatus measure squareness of an end of a rod relative to a longitudinal centerline axis thereof without requiring rotation of the rod. The apparatus includes a flat plate mounted substantially perpendicularly to the rod centerline axis. The method positions the plate in abutting contact with the rod end, and a tilt angle of the plate in abutting contact with the rod end is measured for determining squareness of the rod end.

Abstract: A safety system grade dropped rod detection system for a pressurized water reactor (PWR) utilizes core exit thermocouples arranged in multiple trains and hot and cold leg RTDs to generate a safety system grade rod stop signal. The system generates from the temperature signals a relative power deviation (RD) and a curvature index (CI), which is the spatial second derivative of RD for each fuel assembly. The CI signatures not only provide rapid, reliable detection of dropped control rods, but also clearly identify failed and failing thermocouples.

Abstract: A system for measuring water level includes a reactor pressure vessel containing a core and steam separator assembly, with the vessel being filled with water to a nominal level above the core. A reference leg contains a column of water having a reference level disposed above the nominal level, and a first variable leg has a first tap disposed in the vessel below the reference and nominal levels. A first monitor is disposed between the reference leg and the first leg for determining differential pressure therebetween to indicate level of the water in the vessel above the first tap. A second variable leg includes a second tap in the vessel below the first tap, and a second monitor is disposed between the first and second legs for determining differential pressure therebetween to indicate level of water in the vessel between the first and second taps when the water level falls below the first tap.

Abstract: Apparatus for sensing and transmitting a signal indicative of the position of a movable ferromagnetic member relative to a fixed structure within which the member moves. The apparatus includes a plurality of magnetic circuit arrangements arranged uniformly along the outside of the fixed structure. Each magnetic circuit arrangement includes a pair of magnets and a pair of arcuate-shaped magnetic path elements extending circumferentially about the fixed structure. A plurality of magnetic field responsive position transmitters are positioned adjacent the magnetic circuit arrangements for sensing the presence of the movable ferromagnetic member at predetermined positions within the fixed structure. The apparatus is particularly useful for monitoring the position of control rods in a nuclear reactor because the monitoring is done from outside the sealed structure.

Abstract: A method and a system for fine control of the thermal power of a nuclear boiling water reactor (BWR) with natural circulation. The reactor vessel, in which the core of such a reactor is enclosed, embodies an in-vessel part of a water level gauge containing a water level sensor, such that together with the out-of-vessel part of the system, which is a signal conditioning and processing unit, the effective water level in the vessel can accurately be measured and adjusted either automatically or by hand. The in-vessel part of the system comprises a water level gauge, such as a vertical standpipe, in which the "steam-collapsed" or "effective" water level is accurately created. The effective water level is typically defined for a reactor vessel of a normally operating boiling water reactor (BWR), while partly containing liquid water, partly a mixture of steam and water, and partly just steam.

Abstract: 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.

Abstract: A safety system grade dropped rod detection system for a pressurized water reactor (PWR) utilizes core exit thermocouples arranged in multiple trains and hot and cold leg RTDs to generate a safety system grade rod stop signal. The system generates from the temperature signals a relative power deviation (RD) and a curvature index (CI), which is the spatial second derivative of RD for each fuel assembly. The CI signatures not only provide rapid, reliable detection of dropped control rods, but also clearly identify failed and failing thermocouples.

Abstract: Nuclear reaction detectors capable of position sensitivity with submillimeter resolution in two dimensions are each provided by placing arrays of scintillation or wave length shifting optical fibers formed of a plurality of such optical fibers in a side-by-side relationship in X and Y directions with a layer of nuclear reactive material operatively associated with surface regions of the optical fiber arrays. Each nuclear reaction occurring in the layer of nuclear reactive material produces energetic particles for simultaneously providing a light pulse in a single optical fiber in the X oriented array and in a single optical fiber in the Y oriented array. These pulses of light are transmitted to a signal producing circuit for providing signals indicative of the X-Y coordinates of each nuclear event.

Abstract: Process and device for the positioning of a tool (10) carried by a manipulating arm displaceable in three respectively perpendicular directions of space in relation to the vertical axis of a tube carried by the tube plate of a steam generator for a nuclear reactor. The process involves arranging symmetrically on the arm a set of at least three lighting sources (17) each supplying a light beam directed tangentially towards the periphery of a tube (5), retransmitting, via an optical assembly (18) also carried by the arm, the images of three specific points of the tube illuminated by the sources in the direction of a video monitor, the screen (21) of which comprises three reticles (42, 43, 44) delimiting the actual contour of the tube, and then bringing these images into coincidence with the reticles in order to center the axis (28) of the tools strictly on the axis (35) of the tube.

Abstract: The present invention is a system which determines nuclear reactor control rod axial position using a deviation signature database generated from a current or reference signal pattern produced by one or more strings of axially dispersed fixed incore detector sections in the reactor core. The deviation signature database is produced by assuming deviant axial positions for the control rods in the core, calculating expected detector signals for the assumed positions and storing the deviation of expected signals from a calibration reference along with corresponding assumed rod positions. The signature database is periodically updated to take into account changed core conditions. When a change in detector responses is detected the system performs a signature analysis of the deviations in the signature database using the current deviation from the reference to search for the closest match.

Abstract: Apparatus and method are described for providing a discrete readout of the collapsed water level within a boiling water reactor. An elongate gauge housing is mounted within the reactor vessel extending through the collapsed level from a steam environment into a boiling water environment. A serially coupled sequence of junction defining thermocouple element pairs are positioned within the gauge housing and are arranged with a heating assembly to generate an output signal which corresponds with the water level. Also located under the influence of the heating assembly are reference thermocouples, one providing a reference output corresponding with the instantaneous temperature of the boiling water environment and the other providing a reference output corresponding with the steam environment above the collapsed water level. The signals from the reference thermocouples and the serial coupled level determining thermocouple structures are then treated to define instantaneous water level.

Abstract: 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.

Abstract: Fine and coarse resolvers are used to detect the length of cable withdrawn from a spool to provide an indication of the position of a neutron flux detector at the end of the cable. The position indicated by the resolvers when the neutron flux detector passes a withdrawn limit switch is stored in nonvolatile memory as an offset when the cable is first installed in a flux mapping system. Thereafter, the position indicated by the resolvers, each time the neutron flux detector passes the withdraw limit switch, is compared to the offset. If the difference between the two is significant, a warning is generated, but operation of the flux mapping system continues. During movement of the flux detector, the change in position between two readings of the resolvers is divided by an amount of time measured by a programmable interval timer to determine average speed. A warning is generated if the average speed is outside an expected range. The expected range may vary depending upon the position of the detector.

Abstract: The invention makes it possible to detect and measure the movement of a moving member (50) through an amagnetic or low permeability metal wall. The installation requires ferromagnetic material targets placed at regular intervals over the moving member. The transducer is positioned facing the moving member by its detection face (16). It comprises two ferromagnetic cores (2, 8) surrounded both by an exciting coil (4) and a measuring coil (10), at whose terminals the measuring signal is taken. The latter is proportional to the variable reluctance of the magnetic circuit, which varies as a function of the position of the ferromagnetic targets (48). The transducer is completed by a balancing core (34). Application to the measurement of the displacement of control rods in the vessel of a pressurized water reactor.

Abstract: Disclosed is a device for measuring dimensional characteristics of an elongate component which comprises:(a) an elongate rigid support that bears (i) an upper platform upon which is mounted a drive; (ii) a clamp mechanism for securing said component about its proximal end in a reference position; (iii) a lower platform which supports a pedestal for securing said component about its distal end in a reference position; and(b) a sensor carriage movably mounted to said rigid support and operatively connected to said drive for movement along the elongate extent of said support and having an opening penetrating therethrough for receiving said elongate component when it is secured by and substantially parallel to said rigid support, said carrier bearing a plurality of pivotally-mounted bell cranks spaced about said opening, each bell crank having a wheel for riding on said component during movement of the carrier and being in contact with a sensor capable of providing a signal correlative to displacement of the bell

Abstract: A method of measuring the level of a corrosive, high-pressure, high-temperature liquid in a closed container of a nuclear reactor, by providing a generally tubular structure connected to the closed container of the nuclear reactor so that the level of liquid in the tubular structure is indicative of the level of liquid in the closed container, providing a sealed buoyant float sized to move vertically up an down within the tubular structure, the float being formed of beryllium, detecting from outside the tubular structure the vertical position of said buoyant float, the position corresponding to the level of liquid in the closed container.

Abstract: A method and apparatus for providing a permanent identification of reactor fuel assemblies with an in-reactor remote readout capability. A bar code type code assemblage is permanently coupled with the upper portion of the fuel assembly which is comprised of alternating components of magnetic and non-magnetic metal such as stainless steel. An active sensor including a magnetic core, excitation winding, and sensor or pick-up winding is employed to interact with the individual code components of the bar code assembly. The latter assembly may be formed as a sequence of rings through which the sensor is passed during a grappling procedure or as a sequence of vertically-oriented bar segments positioned outwardly of the fuel assembly and readable by rotating the fuel assembly before the active sensor.

Abstract: A detector path insertion verification system for use with flux mapping of a pressurized water nuclear reactor uses a transfer insertion switch at the input of each multiple-path selector to detect insertion of a detector into the multiple-path selector. No insertion switches are used at the output of the multiple-path selectors; instead software is used to verify the position of the multiple-path selectors. The sensed actual position of each multiple-path selector is monitored as the multiple-path selector is rotated to verify that the sensed actual position passes through the expected sequence of positions in an expected amount of time. The multiple-path selectors are rotated until a sensed actual position is equal to a desired position and rotation is stopped. After the passage of a short period of time, the actual and desired positions are again compared and if equal, insertion is begun.

Abstract: A system for detecting steam voids or bubbles within a reactor coolant system. A dynamic pressure transducer detects pressure fluctuations in the coolant system and produces signals representative of steam voids within the system. The signals produced by the transducer are conditioned and applied as an input to a microprocessor along with other inputs representative of other operating parameters for the reactor coolant system. The microprocessor adjusts the signals representative of steam voids within the system and displays same to the operator.

Abstract: A control road guide tube inspection system is provided which consists of a camera delivery tool which is lowered through the 2.3 inch diameter opening in the guide plates of the tube to position a camera over a selected hole in the guide plate to be inspected. The camera is an underwater CCTV camera, and the system further includes an image enhancement system which uses the video output from the camera to obtain quantitative data on the wear of the guide plates. An ultrasonic gauge to measure the distance from the camera to the guide plate being inspected is also provided on the delivery tool.

Abstract: A system for monitoring an operating condition of a control rod drive mechanism (CRDM) having a pressure housing erectly mounted on a reactor vessel head closure, a vertically movable control rod drive shaft accommodated in the housing and an electromagnetically motive latch mechanism includes an accelerometer fitted to a housing upper end and signal recording means for receiving output signals from the accelerometer through signal processing means and recording the processed output signals.

Abstract: Apparatus for positioning a mast for the inspection and/or repair of a core shroud of a water-cooled nuclear reactor, heretofore have had television cameras directed at centering pins and bores from the side. Due to the inclined direction of surveillance, the alignment produced therewith has been inaccurate. In order to achieve a precise positioning, according to the invention a marking element which is provided between the television camera and the support plate has markings which can be brought into alignment with a marking made on the support plate. The centering pins and the bores are disposed concentrically to one another once they have been brought into alignment.

Abstract: A method is provided for determining and controlling steam water level in a steam generator of a nuclear plant, comprising calibrating the water level sensor in terms of velocity head and also adjusting the high level setpoint in terms of a velocity head bias. The water level differential pressure sensor is calibrated so that maximum water level is indicated as that level corresponding to the upper tap level less velocity head at maximum power plant power. The high level setpoint is calculated as corresponding to the riser level less a velocity head bias, the bias being calculated as maximum velocity head at maximum velocity minus riser head percentage of span times velocity head at maximum power.

Abstract: The rod position indicator system of a pressurized nuclear reactor can be calibrated for one or more control rods without shutdown of the reactor. The procedure involves lowering reactor power to a level at which the control rod which appears to be misaligned can be fully inserted and its rod position indicator calibrated.

Abstract: The reactor core of the plant has tubular vertically movable control rods moved by a pressurized flowing coolant. Each control rod so extends around a tubular guide rod which is immobile relatively to the reactor core as to leave a first annular gap between the control rod and the guide rod. The guide rod interior is operative as a first pressure chamber to which the pressurized coolant is supplied. The top end of each control rod is closed and has a vertical spindle which extends into the guide rod interior and co-operates with the guide rod to bound a second annular gap. At least one first restrictor is disposed in the first annular gap and at least one second restrictor is provided in the second annular gap. A second pressure chamber is present between the two restrictors. The coolant inflowing to the guide rod therefore returns by way of the second annular gap, the second pressure chamber and the first annular chamber to the pressure vessel which extends around the reactor core.

Abstract: A control rod drop monitoring method and apparatus for use in a nuclear reactor including dedicated timers and displays to measure and display the drop time for each control rod when a reactor system trip occurs. The timers and displays may be made from CMOS technology, and may have millisecond resolution, if desired. The timers are initiated upon receipt of one or more reactor trip signals and are halted at the closure of switches for detecting the fully inserted or other preselected position of the control rods in the reactor core. The monitor system is designed for continuous operation. Reactor trip signals and limit switch signals are fed to latch circuits following a trip event or limit switch activation and are unaffected by subsequent changes in the state of the limit switches or trip signals. A manual reset is required to clear rod drop times. Also, a test mode is provided wherein all of the timers can be started and stopped, thereby providing a functional test of 100% of the monitor circuitry.

Abstract: A method for replacing a vessel in a piping system utilizes a template to determine the relative spatial positions of the pipe connections to the vessel in the existing system. The template is then removed from the existing system and reassembled on the new vessel in a remote location to determine the relative spatial position of the new pipe connections to the new vessel to ascertain if alignment will exist between those new pipe connections and the existing pipes in the system. If not, the pipe connections on the new vessel are initially reworked in the remote location to achieve alignment within connection tolerances. The pipes are then cut at their respective connections to the old vessel, the old vessel is removed, the new vessel is put in place in the system and the cut ends of the pipes are connected to new connections on the new vessel to complete the installation of the new vessel in the piping system.

Abstract: The device comprises a rod (28) on which is mounted a means (30, 32, 33) for support and displacement which is movable in an axial direction of the rod (28) and in two directions perpendicular to this axial direction. The support (33) of the means for displacement carries a device for pushing axially on a longitudinal end of the pencil, which may be activated by a control means (35), one end of which is located in a control station (25) disposed above a fuel assembly storage pool. Means for measuring the axial pushing force on the pencil and the length of axial displacement of the pencil under the effect of the pushing are disposed in the control station (25). A video camera (34), carried by the support (33), makes it possible to provide an image of a zone in the vicinity of the end of the pencil.

Abstract: Evaluation for deformations of the channel box of a fuel assembly in a nuclear reactor core in which deformations of the channel box which has been used for exposure so as to be deformed are estimated for future exposure through computation and process of data of core characteristics, data of material properties and shapes of channel boxes, data of initial deformations of the channel box, data of loading patterns and the like, thereby to judge whether the estimated deformations are agreeable for reusing the channel box in the future exposure, or not.

Abstract: The present invention seeks to obtain reliable detection of the fall of a control cluster into the core of a pressurized water nuclear reactor without giving rise to the risk of an erroneous detection causing an untimely emergency reactor stop. Four acquisition units (U1, U2, U3, U4) corresponding to the four quadrants of the reactor core receive neutron flux signals (F1), heat flux signals (P1), and cluster position signals (Z1A, Z1B, . . . ) from the various quadrants and process them to generate corresponding alarm signals. These units, together with a combination circuit (14, 18, 22), provide a cluster fall signal (24) in the presence of at least two alarm signals including at least one cluster position alarm signal. The invention is applicable to electricity power generation.

Abstract: A system for determining the relative positions of control rods within a nuclear reactor is disclosed. When the position signal associated with the highest control rod in a group exceeds the position signal associated with the lowest control rod in the same group by more than a predetermined limit, an alarm and a fault indicator are activated.

Abstract: The instrument for monitoring of the cooling conditions in the reactor core of a light water reactor includes a probe (2), which is introduced into the reactor vessel and comprises a casing (12) made from a low neutron absorbing and water-resistant material, a resistor (11) being hermetically enclosed in the casing (12). The resistor (11) is connected to power supply lines (5). The resistance of the resistor (11) is dependent on the temperature of the resistor. The instrument also includes sensing means providing an output signal, which is dependent on the resistance of the resistor (11), when current flows through the same.In a first mode of operation the monitor is used for detection of a reduction or loss of cooling capacity of the coolant surrounding the probe (2).

Abstract: In a boiling water nuclear reactor having its core, fuel support casting, and control rod guide tubes removed to expose the core plate, an apparatus and method for the repair and replacement of the control rod drive housing at the bottom extremity of the reactor vessel is disclosed. The apparatus registers to a hole in the core plate and its corresponding guide pin. A mating fixture on the depending extremity of the shaft of the apparatus precisely fits and mates to the top of the control rod drive housing. The alignment device includes cross electronic levels sealed for submersion which levels remotely transfer through attached wiring the precise angularity between the top of the control rod drive housing on one hand and the corresponding and overlying hole in the core plate on the other hand.

Abstract: A snubber monitoring system is provided for a nuclear power plant wherein the snubbers are disposed at various locations within a plant containment structure to support piping and equipment rigidly against seismic and vibratory loading while permitting thermal expansion and contraction thereof. The system includes displacement sensing means and temperature sensing means coupled to each of the snubbers to generate continuous snubber displacement and pipe and equipment temperature signals.A sensor data highway system has cable connected data collectors disposed within the plant containment to collect the snubber sensor signals. A receiver and a programmed computer system are located outside the containment to process the snubber displacement and pipe and equipment temperature signals to provide substantially continuous snubber monitoring. A data highway cable extends through the containment to couple the signal collectors to the receiver and computer system.