Abstract: An integrated information system is provided for a plant with interactive processes running in functional equipment subsets, such as a nuclear power generation plant. Sensors are operatively coupled to monitor processes and equipment in the plant, collecting sample data for assessing operational conditions and for predicting maintenance requirements based on loading of the equipment. One or more processors access the sample data and compares present conditions to diagnostic specifications, technical specifications and historical data stored in memory and indexed to equipment subsets and functional operating groups. The processor(s) generate prioritized reports to alert users to potential operational and/or maintenance problems. In addition to the prioritized reports, the processor accesses and outputs to the users reports of the diagnostic and technical specifications applicable to the process parameters exhibiting the potential problems.

Abstract: An automated monitoring system and method of operation is provided for a nuclear reactor having a pressure vessel containing a reactor core for boiling water to generate steam. A plurality of monitors provide signals for respective monitoring parameters for monitoring operation of the reactor, and a computer includes a database therein containing predetermined setpoints for the monitoring parameters. The computer identifies abnormal and normal behavior of the monitoring parameters based on the database, and determines cause of abnormal behavior of the monitoring parameters using artificial intelligence. A warning i also provided to identify the cause of the monitoring parameter abnormal behavior. And, automatic mitigation action may also be effected.

Abstract: A multicontroller apparatus has a plurality of control units each including a controller and a diagnostic device for making a diagnosis of the controller. Each diagnostic device includes an apparatus for judging states of other control units by using output signals of diagnostic devices included in the other control units and an apparatus for executing a diagnosis of the associated controller which is a diagnosis object of the diagnostic device when the judging apparatus has judged that one or more other control units are not in the diagnosis state. Owing to the present invention, a necessary number of controllers which are in the controllable state can always be ensured in a multicontroller apparatus. Therefore, control by the multicontroller apparatus is always possible, and it becomes possible to make a diagnosis upon the multicontroller apparatus.

Abstract: Replacing regular mesh-dependent ray tracing modules in a collision/transfer probability (CTP) code with a ray tracing module based upon combinatorial geometry of a modified geometrical module (GMC) provides a general geometry transfer theory code in two dimensions (2D) for analyzing nuclear reactor design and control. The primary modification of the GMC module involves generation of a fixed inner frame and a rotating outer frame, where the inner frame contains all reactor regions of interest, e.g., part of a reactor assembly, an assembly, or several assemblies, and the outer frame, with a set of parallel equidistant rays (lines) attached to it, rotates around the inner frame.

Abstract: An expert system for online surveillance of nuclear reactor coolant pumps. This system provides a means for early detection of pump or sensor degradation. Degradation is determined through the use of a statistical analysis technique, sequential probability ratio test, applied to information from several sensors which are responsive to differing physical parameters. The results of sequential testing of the data provide the operator with an early warning of possible sensor or pump failure.

Abstract: A system for improving the performance of nuclear power plant feedwater control systems and simplifying steam generator low water level reactor protection logic includes a plurality of water level channels for measuring steam generator water level and generating a plurality of signals representative thereof. The median steam generator water level signal is selected from among the plurality of steam generator water level signals. The median steam generator water level signal is then communicated to the feedwater control system through an output interface.

Abstract: An emergency stop of a pressurized water reactor to be protected is triggered when the nuclear power (ET) thereof reaches an emergency stop limit (LP). The value of this limit is lower with lower operating temperatures (ST) of the reactor.

Abstract: In an apparatus including a fluid circulation unit for allowing a fluid in a container to be circulated along a passage in the container, a flow rate measuring apparatus includes a rotational speed transducer for detecting the rotational speed of a motor for driving the fluid circulation unit and a pipe network model calculator for receiving a rotational speed signal from the rotational speed transducer. The model calculator has an initially programmed pipe network model corresponding to flows in the container and calculates the flow rate at a corresponding location of the model with the rotational speed of the circulation unit replaced by constants of the model and hence calculates a flow rate of the fluid at that location in a real passage.

Abstract: A multiplex control system has a plurality of control apparatuses, test signal generators provided, respectively, for the control apparatuses for the purpose of internal diagnosis thereof, signal selectors each for selecting a signal to operate a device under control from the signals produced by the control apparatuses, and diagnosis units each for deciding presence or absence of abnormality in the associated signal selector with the aid of the signals inputted to the signal selector and the output signal therefrom.

Abstract: The present invention is a computer based system supporting plant operators in caring out nearly routine operations. The computer based system monitors available plant instrumentation signals and processes the gathered information to detect satisfaction of initial conditions to the state change. Once the state change is started, the system then compares the sequence of observed changes in the plant with a preprogrammed sequence and alerts the operators to any undesirable deviations from the preplanned sequence by providing appropriate attention grabbing displays on a system monitor. The system also continuously monitors constraining conditions and alerts the operator when the system moves toward an undesired state. The system requires no input from the operator when the operation underway is following the prescribed sequence and minimal input from the operator when a deviation is detected. The system internally and automatically tracks the evolution of plant states during the nearly routine operations.

Abstract: Control clusters, each of which comprises a plurality of neutron-absorbing rods, are operable by means of electromagnetic mechanisms whose coils are powered by power bridges driven from a control desk (11). The control system includes a controlling hard-wired logic circuit (12) serving the desk and supervising a plurality of hard-wired logic interfaces each of which serves a subgroup (10) of electromagnetic mechanisms for a determined number of clusters. The static power assemblies (9) each including a hard-wired logic interface and the power bridges of the subgroup(s) (10) served thereby are successively and independently replaced by at least one electronic power assembly (23) constituted by a computer and the power bridges of a subgroup served thereby.

Abstract: A plant malfunction diagnostic method is characterized by determining by simulation a change in a plant state variable, forming a pattern among plant state variables obtained by autoregressive analysis of the change in plant state variable, inserting the formed pattern among the plant state variables in a neural network, performing learning until a preset precision is obtained, and identifying the cause of the malfunction by inserting, in the neural network, a pattern which indicates the pattern among plant state variables formed by data gathered from the plant. This makes possible early identification of the cause of a malfunction. Plant rate of operation and safety are improved by allowing the operator to perform the appropriate recovery operation with a sufficient time margin.

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: 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 multiplex control system has a plurality of control apparatuses, test signal generators provided, respectively, for the control apparatuses for the purpose of internal diagnosis thereof, signal selectors each for selecting a signal to operate a device under control form the signals produced by the control apparatuses, and diagnosis unit each for deciding presence or absence of abnormality in the associated signal selector with the aid of the signals inputted to the signal selector and the output signal therefrom.

Abstract: Protection against the consequences of a cluster of control rods falling accidentally is provided by four chains, each of which includes two neutron flux detectors (D1A, D1B), two primary treatment circuits (R1A, S1A and R1B, S1B) associated with said two detectors such that each provides a primary fall signal in the event of the flux measured by the corresponding detector decreasing rapidly, and an OR gate (P1) for providing an output fall signal from the chain in the event of at least one of said primary signals being present. The detectors (D1A, D4B, D3A, D1B, D2A, D3B, D4A and D2B) are angularly distributed around the vertical axis (A) of the core (2). A secondary treatment circuit (6) causes an emergency reactor stop to take place in the event that it receives fall signals at the outputs from at least two chains.

Abstract: A control system for a nuclear steam power plant having a reactor, one or more once through steam generators and a turbine includes a reactor control subsystem responsive to a power demand input to cause the reactor to deliver thermal power commensurate with the power demand input to the once through steam generator, one or more feedwater control subsystems sensing the thermal power delivered by the reactor to control feedwater flow to the once through steam generator, such as via a regulating valve and/or a feed pump, to match the thermal power delivered by the once through steam generator to the turbine with the thermal power delivered by the reactor, and a turbine steam demand control subsystem responsive to the thermal power delivered by the once through steam generator by sensing steam pressure to control a governor valve to admit steam to the turbine to cause the turbine operation to match the steam supplied by the once through steam generator such that the nuclear steam power plant is plant process con

Abstract: An interactive display apparatus and method for a plant operating at a plurality of process parametes from which a current plant status can be calculated, and from which symptoms can be diagnosed which indicate the existence of transient conditions of plant status for which mitigating action must be taken within a time interval, utilize a central computer for storing all appropriate mitigating actions which should be taken upon the occurrence of a symptom. The computer is also programmed with algorithms for selecting and prioritizing mitigating actions that are appropriate. A display is connected to the computer for displaying the list of mitigating actions which are appropriate for a symptom diagnosed by the central computer. Sets of symptom indicators and extreme action indicators are also driven by the computer. Each symptom is represented by a separate card which can be independently illuminated to indicate the existence of that symptom.

Abstract: Dynamic logic units utilize magnetic cores of rectangular hysteresis loop material wound with an input winding, a pair of output windings connected to a CMOS flip-flop, and a d-c control winding. With a d-c current on the control winding, the core experiences flux reversals in response to a square wave on the input winding to generate output pulses which alternately switch the flip-flop to produce a square wave output which matches the input. In a first embodiment, the output windings are in the form of a center-tapped winding with the center tap grounded to provide a low impedance discharge path for the capacitors in grounded R-C filters on the inputs to the flip-flop which suppress voltage spikes. In a second embodiment, output windings on separate magnetic cores which share an input windings but only one of which has a control winding, are connected in opposition to eliminate the switching spikes in the signal applied to the flip-flop.

Abstract: The invention improves detecting that a control cluster has fallen into the reactor of a nuclear fission power station. Variations are monitored firstly in the nuclear power (3) and secondly in at least one parameter (1, 2) external to the reactor and having an influence on reactor control. A cluster is considered as having fallen when a rapid drop (12j) is detected in said power while no variation (12a, 12b, . . . 12h) is simultaneously detected in an external parameter that could have given rise to said power drop.Application to producing electricity.

Abstract: A safety control safeguard system includes sensors disposed in a quadruple array. First, second, third and fourth signal processing channels provided in parallel each include signal processing means for receiving output signals from the associated sensors for producing a trip signal. First and second actuating means operable independent of each other are provided for actuating an apparatus to be controlled. A first switch means operatively connected to the first, second, third and fourth processing channels for activating the first actuating means in response to reception of the trip signal produced by the signal processing channels and second switch means operatively connected to the first, second, third and fourth processing channels for activating the second actuating means in response to reception of the trip signal produced by the signal processing channels.

Abstract: The low alarm threshold (B) of the overheating ratio of a nuclear reactor is determined in such a manner that the higher the position of the temperature-regulating rods, the lower the value determined for said threshold. The invention is applicable, in particular, to pressurized water nuclear reactors used for producing electrical power.

Abstract: A system for variably delaying reactor trip and auxiliary feedwater system actuation resulting from a low water condition in a steam generator includes a plurality of sensors for determining both whether a low water condition exists in each steam generator and the power output level of the reactor. The length of the variable time delay is determined based upon the severity of the steam generator low water level condition and the reactor power output level. The reactor is then tripped and the auxiliary feedwater system actuated at the expiration of the time delay period if the steam generator water level is not restored.

Abstract: Signals from redundant sensors located throughout a pressurized water reactor (PWR) nuclear power plant are processed in four independent channel sets each of which includes a plurality of independent microcomputers which calibrate, convert to engineering units and calculate partial trip signals and engineered safeguard actuation signals from the sensor signals for use in the conventional voting logic of a plant protection system. The primary and secondary partial trip and engineered safeguard actuation functions associated with various postulated abnormal events are allocated to different independent microcomputers in the channel set for reliability. A test unit common to the channel set automatically, rapidly bypasses and tests each protection function independently while the other protection functions in the channel set remain on-line and also continually tests each microcomputer through a dummy test function performed along with the assigned protection functions.

Abstract: The present invention relates to a signal selector which selects a signal for control of various operating parameters in a process facility. The system includes a display and first and second sensors each providing a signal representative of a single controlled parameter. The first signal is preferred as a control signal for the parameter. A switch is arranged on the display for manually selecting between the first and second signals or for selecting an automatic selection mode. The system further includes an arrangement for determining if the first signal is unacceptable including comparing the first and second signals to one another and to a first pre-selected threshold value and either by comparing the first signal to a second threshold value or performing a second comparison of the two signals. The system automatically switches to the second signal when the first signal is unacceptable when the switch is in the automatic selection mode.

Abstract: A rod drive control system for nuclear such as boiling water reactors is comprised of a plurality of stepping motors for inserting and withdrawing control rods disposed within the nuclear reactor, which the stepping motors are each provided for each control rod, terminal units which are each provided for each stepping motor and are each provided with a motor controller to drive the related stepping motor and to check the operation of the motor, a central processing unit for transferring an operation signal to the motor control unit and for detecting faults in the terminal units, and transmission lines between the terminal units and the central processing unit.

Abstract: A self-testing contact closure test circuit and method in which invalid logic states are artificially created in order to simulate a switch malfunction, and thus to determine whether the testing circuitry correctly identifies the invalid state. The system is designed to be used with switches such as those incorporating form "C" arrangements having two pairs of contacts which under normal circumstances are in opposite states.

Abstract: A control system for a trip coil in a switchgear mechanism which controls the supply of power to a process control device and ensures de-energization of the trip coil shortly after the trip coil is energized. A transformer is supplied with power by the switchgear and outputs reduced power to a rectifier which is connected to the trip coil via a trip activation device. The output of the rectifier can be monitored to determine the ability of the control system to activate the trip coil and the condition of the power supplied to the process control device.

Abstract: A calibrator for a pressurized water reactor (PWR) core predictor utilizing a distribution expression for the transverse buckling factor, in a one dimensional diffusion model, which has coefficients correlated with overall neutron balance and with a set of power distribution characterization parameters including axial offset, axial pinch, axial quarters and axial fifths. The coefficients are periodically adjusted incrementally one at a time to produce criticality with the model at measured values of rod position, reactor power level, cold leg temperature and boron concentration until the power distribution characterization parameters calculated from a power distribution generated by the model are within preset tolerances of those from a power distribution measurement generated by movable, or if provided, fixed, incore detectors.

Abstract: The setpoints for control systems in a pressurized water reactor are adjusted by an amount corresponding to the expected change in the controlled process variable resulting from rapid fluctuations in load to reduce the duty time of the control system components such as the rod drive mechanisms in the rod control system and the spray and heater units in the pressurizer pressure control system. In addition, the deadband in the response of the rod control system is continuously varied as a function of the variance of the magnitude of the rapid fluctuations in load to further reduce wear while maintaining good response during load following.

Abstract: A power interface circuit periodically which receives test pulses to test the operation and connections thereof. Voltage and current sensors detect the result of the testing and may be used for zero-crossing detection when AC powered devices are controlled by the power interface circuit. Preferrably, asymmetrical pulses, such as those representing an ASCII character, are used as the test pulses. Three input signals are received by the power interface circuit which performs two out of the three voting on the input signals to generate a control signal for two power switches. The power switches may be connected in parallel or in series to provide additional fault tolerance.

Abstract: In a protection system for a complex process control system which generates three independent actuation signals, the power circuit includes three pairs of switches arranged in three groups connected in series with each other and with a load device and a voltage source. Each group of switches includes two switches selected from different pairs of switches and connected in parallel. The same circuit topography is used for normally energized and normally deenergized loads with normally closed siwtches used with the former and normally open switches used with the latter. For testing the circuit, each group of switches is shunted by a resistor to form a leakage path through the configuration of switches. The impedance of each resistor is several times that of a closed switch such that the leakage current is insufficient to energize the load, but sufficient to be detected by a current detector which measures the current drawn from the voltage source.

Abstract: The present invention relates to a method and apparatus for testing analog process protection and control systems which are composed of a plurality of channels each serving to monitor a selected process parameter.

Abstract: Each of the either normally closed or normally open switches, in an n out of m voted power interface circuit having parallel connected groups of serially connected switches, is shunted by a high impedance resistor to form a leakage path through each group of switches. A detector associated with each group of switches, and responsive to the change of impedance produced by actuation of a resistor shunted switch in the group, generates an output signal, preferably a one bit digital signal, indicative of the state of the switches in the group in response to a sequence of test signals which selectively actuate fewer switches than are required to actuate the load controlled by the power interface. Compensation for large variations in supply voltage is provided by incorporating each group of switches into a resistance measuring bridge circuit in which the digital output signal is generated by a comparator connected across the bridge. Preferably, the bridge circuits share common reference voltage generating legs.

Abstract: A method of operating a pressurized water nuclear reactor comprising determining the present core power and reactivity levels and predicting the change in such levels due to displacer rod movements. Groups or single clusters of displacer rods can be inserted or withdrawn based on the predicted core power and reactivity levels to change the core power level and power distribution thereby providing load follow capability, without changing control rod positions or coolant boron concentrations.

Abstract: A power interface circuit for normally deenergized loads includes the capability to test the operation and connections thereof without any possibility of accidental activation of the load. Three input signals may be received by the power interface circuit which supplies power to a load if two out of three of the input signals indicates activation of the load. A normally closed switch which ordinarily provides power directly to the voter is opened during testing so that the voter is supplied with a reduced power that is insufficient to activate the load. The normally closed switch is closed if any of the input signals indicate activation of the load. Current sensors are included in the power interface circuit to detect all possible logic combinations for activating the load and to detect the operation of the normally closed switch.

Abstract: A rod position indicating system for a pressurized water reactor generates within containment redundant sets of digital detector signals and applies both sets to each of two communications buses each controlled by a separate bus controller/serial output device located inside of containment. A pair of redundant serial data links transmits the redundant data from each bus controller/serial output device through containment to a dedicated CRT display and the plant computer each of which generates rod position displays from redundant information selected from one of the data links. The data for each rod is selected individually from the redundant signals received on the one data link. Rod position is presented in bargraph form on a multi-page display which includes overall status information along with the detailed presentations.

Abstract: In a protection system for a complex process control system which generates three independent actuation signals, the power interface circuit includes three pairs of switches arranged in three parallel groups of switches connected in series with the load and a voltage source. Each group of switches includes two switches selected from different pairs of switches and connected in series. Normally closed switches are used with normally energized loads and normally open switches with normally de-energized loads. Logic gates control actuation of each individual switch in response either to an associated actuation signal or a test signal generated by a microprocessor. The microprocessor generates a sequence of patterns of test signals which result in various combinations of switch actuations. The current through each group of switches resulting from each combination of switch actuations is compared by the microprocessor with expected values to evaluate circuit performance.

Abstract: The dynamic logic of each channel of a multichannel protection system for a nuclear power plant provides a trip logic path and a global bypass logic path by which pulse signals from a clock source may be transmitted to a dc-to-dc power converter which energizes the undervoltage coils for a pair of contactors in the reactor trip switchgear. Each of the logic paths is constructed of basic logic units which in turn, each include a toroidal core of rectangular hysteresis loop magnetic material having a control winding which must be energized by a dc current in order for pulses applied to an input winding to appear at an output winding. Blockage of pulses through any one of the serially connected basic logic units in a logic path terminates the flow of pulses to the converter through that logic path. The control windings of corresponding logic units of the trip logic path in each channel are energized by one of a set of redundant sensors which monitor one of a plurality of reactor trip parameters.

Abstract: An analog output network provides multiple communication paths for control of an actuator in response to an input signal. The analog output network includes at least two controllers, each of which is connected to an analog output circuit and a controller selector which is connected to each of the controllers and the analog output circuits. The controller selector ensures that at least one of the analog output circuits is enabled at all times and identifies one of the controllers as an on-line controller. The analog output circuit connected to the on-line controller generates an actuation signal which passes through the actuator and the other analog output circuit. An alternate current path comprising a diode string with a voltage drop larger than the voltage drop of the actuation signal in the other analog output circuit is provided so that if an analog output circuit is removed or defective, the actuation signal from the on-line analog output circuit is still provided with a current path.

Abstract: On-line, real time monitoring of core-wide and local power in an advanced pressurized water reactor is provided by a system having four channel sets of fixed incore nuclear detector strings distributed in fuel assemblies across the core in a pattern which produces a uniquely identifiable detector response to rod movement even with one channel set out of service. Separate signal processors for each channel generate totally independent core-wide overpower protection signals and exchange detector responses through fiber optic data links for local power monitoring. The local power density at each detector level for any desired point across the core is determined by fitting a surface spline function to the detector responses adjusted to eliminate the local effects of rod movement from a reference condition, interpolation of the fitting function, and factoring back in the local effects of rod movement.

Abstract: Process and device for the detection of the variations, due to a fault in the position of the core control clusters, in the reactivity of the core of a reactor. A momentary value (6) representing the reactivity calculated directly from the core neutron power (2) is compared to a momentary value (30) representing the reactivity calculated from the momentary mean temperature (25) in the core and the mean boron concentration (29) in the primary fluid passing through the core. The invention applies to pressurized water nuclear reactors.

Abstract: Process and device for the detecting of faults in the distribution of the power of the core (2) of a pressurized water nuclear reactor, in which at least one parameter representing the power of the core (2) is measured, each parameter being measured at a determined number of points. For each parameter, the difference between the two extreme measured values and the ratio of this difference to the smallest measured value are determined, and this ratio is compared to a set value, a fault being detected if this ratio is greater than the set value. The sensors (4, 9) are arranged symmetrically close to the periphery of the core (2) and a further sensor (9) is placed close to the center of the core (2).

Abstract: Safety actuator release device incorporating a release means, whereof one output supplies an output signal which can have two logic states, one of these states corresponding to the release of the actuator and the other state corresponding to the absence of the release of the actuator, testing and control means of said release means, whereby said testing and control means have two control inputs receiving the control signals from the release means in order that the output signal has one of two logic states and a test input receiving a test signal in such a way that said output supplies an output signal, whose logic state corresponds to the release of the actuator, even if the control signals lead to the supply of an output signal corresponding to the absence of release, wherein the testing and control means are constituted by three primary windings of a magnetic amplifier, two of these primary windings receiving direct currents corresponding to the control signals, while another of these windings is a test win

Abstract: An inadvertent approach to criticality in a nuclear fueled electric power generating unit is detected and an alarm is generated through on-line monitoring of the neutron flux. The difficulties of accurately measuring the low levels of neutron flux in a subcritical reactor are overcome by the use of a microcomputer which continuously generates average flux count rate signals for incremental time periods from thousands of samples taken during each such period and which serially stores the average flux count rate signals for a preselected time interval. At the end of each incremental time period, the microcomputer compares the latest average flux count rate signal with the oldest, and preferably each of the intervening stored values, and if it exceeds any of them by at least a preselected multiplication factor, an alarm is generated.

Abstract: A universal logic card is disclosed which contains both pre-programmed functional circuitry for actuating channel logic and dedicated test circuitry for system controller test and for constant and looping interrogation of the pre-programmed channel logic in absence of self-test system controller test. The disclosed card resides as a channel in a self-test system for a nuclear power plant supplementing the nuclear reaction protection system. The card is pre-programmed in digital logic to act equivalent to an analog circuit during actual plant operation. Additionally, the card responds to system controlled surveillance of the nuclear protection system. In system controlled surveillance, a central microprocessor serially addresses system circuit cards such as the one disclosed and loads these cards at predetermined input points with test commands. The addressed cards are thereafter simultaneously activated by a system-wide command.

Abstract: A logic safety system is disclosed having four redundant channels with each channel constituted by a logic circuit for controlling the triggering of a protective action, a logic alarm circuit connected to the control circuit and a logic inhibition circuit which makes it impossible to simultaneously inhibit several alarm circuits. Any attempt at inhibiting the alarm circuit of a second channel while an alarm circuit of a first channel is already inhibited will result in the automatic appearance of a protective action control signal at the output of the second channel regardless of the signal received at the input of the alarm circuit of the second channel.

Abstract: The present invention relates to a device for controlling the dimensions and spaced-apart relationship of rigid pieces disposed in a bundle. Said device comprises: two supple probes adapted to transmit a light beam and insertable between rows of pieces so as to surround one of these rows; means for positioning and displacing these probes; a source of light emitting a light beam transmitted by the first probe then picked up by the second transmitting it to a photodetector producing an electrical signal; electronic means for processing this signal, furnishing information making it possible to control, from reference values, the dimensions and spaced apart relationship of the pieces, due to the modulation of said signal, provoked by the successive occultations of the light beam by the pieces, during the displacement of the probes along the row of pieces. The invention is applicable to the control of the pencils of a fuel assembly of a nuclear reactor.

Abstract: A trip system comprises groups of three switches, each group being responsive to a single trip initiating event and each switch switching a different phase of a three phase power supply. Three trip actuators are each connected between different pairs of switches. Malfunction of a single switch in any group will not cause a trip to occur while concurrent operation of two or more switches in any group will cause a trip.

Abstract: When monitoring the period of a nuclear reactor, a signal representing the reactor power is generated and compared with a reference signal. When a difference between the power signal and the reference signal is detected, the level of the reference signal is changed at a predetermined rate independent of the magnitude of said difference in a direction to reduce said difference. Hereby the reference signal is brought to follow the power signal as long as the latter does not change faster than said predetermined rate of change for the reference signal. At least one warning level signal is generated, the level of which being equal to the instant level of the reference signal multiplied by a predetermined factor greater than one. The power signal is compared also with this warning level signal, and a warning signal is generated when the level of the power signal becomes equal to or exceeds the level of said warning level signal.