A method for estimating a quantity of a system includes the following steps: for each variable of a plurality of variables, obtaining a sequence of successive measurements, determining a sequence of successive values of a stability parameter, the parameter being a weighted sum of rates of variation of the variables, identifying a time interval in which the stability parameter is less than or equal to a predetermined threshold for a duration greater than or equal to a predetermined duration, estimating a sequence of successive estimates of a particular variable, a start time of the sequence being included in the time interval, comparing the sequence of estimates and the sequence of measurements, in order to determine an adjustment parameter, and estimating the physical quantity of the system using the adjustment parameter.

A method for estimating a quantity of a system includes the following steps: for each variable of a plurality of variables, obtaining a sequence of successive measurements, determining a sequence of successive values of a stability parameter, the parameter being a weighted sum of rates of variation of the variables, identifying a time interval in which the stability parameter is less than or equal to a predetermined threshold for a duration greater than or equal to a predetermined duration, estimating a sequence of successive estimates of a particular variable, a start time of the sequence being included in the time interval, comparing the sequence of estimates and the sequence of measurements, in order to determine an adjustment parameter, and estimating the physical quantity of the system using the adjustment parameter.

A method for determining a state of operational readiness of a fuel cell backup system of a nuclear reactor system includes monitoring a readiness state of a fuel cell system associated with a nuclear reactor system, and providing a readiness determination of the fuel cell system by comparing the monitored state of readiness of the fuel cell system to an established operating readiness state, the established operating readiness state a function of at least one characteristic of the nuclear reactor system. An apparatus includes a fuel cell monitoring system configured to monitor a readiness state of a fuel cell system associated with a nuclear reactor system, and a readiness determination system configured to provide a readiness determination of the fuel cell system by comparing the monitored state of readiness of the fuel cell system to an established operating readiness state.

A method for determining a state of operational readiness of a fuel cell backup system of a nuclear reactor system includes monitoring a readiness state of a fuel cell system associated with a nuclear reactor system, and providing a readiness determination of the fuel cell system by comparing the monitored state of readiness of the fuel cell system to an established operating readiness state, the established operating readiness state a function of at least one characteristic of the nuclear reactor system. An apparatus includes a fuel cell monitoring system configured to monitor a readiness state of a fuel cell system associated with a nuclear reactor system, and a readiness determination system configured to provide a readiness determination of the fuel cell system by comparing the monitored state of readiness of the fuel cell system to an established operating readiness state.

A method and system for calibrating nuclear instrumentation of a reactor is disclosed. The system comprises a reactor configured to operate at a low power level and an external heater configured to heat the reactor to its operating temperature and maintain the reactor in a critical state. The reactor maintains its temperature at a steady state by repeating steps of reducing the heater's power and increasing the reactor's power by changing one or more reactivity settings, wherein the reduced heater's power is compensated by using the increased power generated by the reactor itself. The nuclear instrumentation is configured to measure the reactor's output power and compare it with the calculated reactor's power. Based on the discrepancy between the calculated power and the measured power exceeds a threshold; and the nuclear instrumentation is appropriately calibrated by adjusting one or more settings.

The present invention relates to a passive nitrogen injecting device for a nuclear reactor coolant pump, the device comprising: a nitrogen supply unit for supplying nitrogen; a pressure control valve for controlling the supply of nitrogen from the nitrogen supply unit according to pressure; an accumulator for filling the nitrogen supplied through the pressure control valve at a set pressure, and supplying the filled nitrogen in the event that an accident involving coolant loss occurs; and an isolation valve for controlling the supply of the nitrogen from the accumulator into a seal housing of a nuclear reactor coolant pump. The present invention uses an accumulator so as to be able to supply nitrogen by using the pressure in the accumulator without the supply of external power in the event of an accident involving coolant loss, and therefore has the effect of being able to improve safety.

A critical heat flux prediction device, a critical heat flux prediction method, a safety evaluation system, and a core monitoring system using the safety evaluation system can predict critical heat flux in a core of a reactor with a high degree of accuracy by obtaining a correlation plot distribution representing a relation of critical heat flux on a thermal equilibrium quality based on experimental data, approximating a correlation plot distribution through a logistic function that is a model function in which critical heat flux is expressed by a function of a thermal equilibrium quality, and obtaining a critical heat flux correlation of critical heat flux and a thermal equilibrium quality.

An apparatus for detecting a position of a control rod includes a control rod driving shaft having an outer circumferential surface on which position information is marked, a mirror configured to reflect the position information, and a detector configured to detect a position of the control rod driving shaft from the position information reflected from the mirror, when the control rod driving shaft moves vertically.

A method for measuring position of a translational movable element of a nuclear reactor, includes emitting kN optical signals, k and N being natural numbers greater than or equal to 1, by kN so-called emitter optical fibres included in N probes resistant to a primary medium; receiving the kN optical signals by N tracks resistant to a primary medium, each track receiving k optical signals, the tracks having reflecting surfaces and diffusing surfaces; receiving, by mN so-called receiver optical fibres, m being a natural number greater than or equal to k, included in the N probes, the kN optical signals reflected or diffused by the N tracks; converting the kN optical signals received by the mN receiver optical fibres into binary code.

A method and system for calibrating nuclear instrumentation of a reactor is disclosed. The system comprises a reactor configured to operate at a low power level and an external heater configured to heat the reactor to its operating temperature and maintain the reactor in a critical state. The reactor maintains its temperature at a steady state by repeating steps of reducing the heater's power and increasing the reactor's power by changing one or more reactivity settings, wherein the reduced heater's power is compensated by using the increased power generated by the reactor itself. The nuclear instrumentation is configured to measure the reactor's output power and compare it with the calculated reactor's power. Based on the discrepancy between the calculated power and the measured power exceeds a threshold; and the nuclear instrumentation is appropriately calibrated by adjusting one or more settings.